diff --git a/.github/workflows/label-cherry-pick.yaml b/.github/workflows/label-cherry-pick.yaml
index 3b9c03d5d779..f58d0a458944 100644
--- a/.github/workflows/label-cherry-pick.yaml
+++ b/.github/workflows/label-cherry-pick.yaml
@@ -58,6 +58,7 @@ jobs:
       REPOSITORY: ${{ github.repository }}
       GITHUB_REF: ${{ github.ref }}
       MERGE_COMMIT_SHA: ${{ github.event.pull_request.merge_commit_sha }}
+      CHERRY_PICK_BRANCH: cherry-pick-${{ matrix.target_branch }}-${{ github.event.pull_request.number }}
     steps:
       - name: Checkout repository
         uses: kaidokert/checkout@v3.5.999
@@ -101,7 +102,7 @@ jobs:
           token: ${{ secrets.CHERRY_PICK_TOKEN }}
           draft: ${{ steps.cherry-pick.outcome == 'failure' }}
           base: ${{ matrix.target_branch }}
-          branch: "cherry-pick-${{ matrix.target_branch }}-${{ github.event.pull_request.number }}"
+          branch: ${{ env.CHERRY_PICK_BRANCH }}
           committer: GitHub Release Automation <github@google.com>
           reviewers: ${{ github.event.pull_request.user.login }}
           title: "Cherry pick PR #${{ github.event.pull_request.number }}: ${{ github.event.pull_request.title }}"
@@ -129,6 +130,6 @@ jobs:
                 issue_number: '${{ steps.create-pr.outputs.pull-request-number }}',
                 owner: context.repo.owner,
                 repo: context.repo.repo,
-                body: '> [!IMPORTANT]\n> There were merge conflicts while cherry picking! Check out the PR branch (${{ matrix.target_branch }}-${{ github.event.pull_request.number }}) and fix the conflicts before proceeding. Check the log at ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }} for details.'
+                body: '> [!IMPORTANT]\n> There were merge conflicts while cherry picking! Check out [${{ env.CHERRY_PICK_BRANCH }}](${{ github.repository }}/tree/${{ env.CHERRY_PICK_BRANCH }}) and fix the conflicts before proceeding. Check the log at ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }} for details.'
               });
             }
diff --git a/base/strings/string_util.h b/base/strings/string_util.h
index 31975a4ec978..be7000249f4b 100644
--- a/base/strings/string_util.h
+++ b/base/strings/string_util.h
@@ -9,7 +9,9 @@
 
 #include <ctype.h>
 #include <stdarg.h>   // va_list
+#if SB_API_VERSION >= 16
 #include <stdio.h>
+#endif
 
 #include <initializer_list>
 #include <string>
diff --git a/base/strings/string_util_starboard.h b/base/strings/string_util_starboard.h
index bace97556527..cdce542fbf3b 100644
--- a/base/strings/string_util_starboard.h
+++ b/base/strings/string_util_starboard.h
@@ -25,6 +25,11 @@
 
 namespace base {
 
+inline int vsnprintf(char* buffer, size_t size,
+                     const char* format, va_list arguments) {
+  return ::vsnprintf(buffer, size, format, arguments);
+}
+
 inline int strncmp16(const char16* s1, const char16* s2, size_t count) {
 #if defined(WCHAR_T_IS_UTF16)
   return wcsncmp(s1, s2, count);
diff --git a/base/strings/stringprintf.cc b/base/strings/stringprintf.cc
index f371b37d81df..c260b9ce0542 100644
--- a/base/strings/stringprintf.cc
+++ b/base/strings/stringprintf.cc
@@ -29,7 +29,7 @@ inline int vsnprintfT(char* buffer,
                       size_t buf_size,
                       const char* format,
                       va_list argptr) {
-  return ::vsnprintf(buffer, buf_size, format, argptr);
+  return base::vsnprintf(buffer, buf_size, format, argptr);
 }
 
 #if defined(OS_WIN)
diff --git a/cobalt/browser/application.cc b/cobalt/browser/application.cc
index 7c33e71a19c5..1f73882376c2 100644
--- a/cobalt/browser/application.cc
+++ b/cobalt/browser/application.cc
@@ -116,7 +116,7 @@ const int64_t kWatchdogTimeInterval = 10000000;
 const int64_t kWatchdogTimeWait = 2000000;
 
 bool IsStringNone(const std::string& str) {
-  return !base::strcasecmp(str.c_str(), "none");
+  return !strcasecmp(str.c_str(), "none");
 }
 
 #if defined(ENABLE_WEBDRIVER) || defined(ENABLE_DEBUGGER)
diff --git a/cobalt/csp/source_list.cc b/cobalt/csp/source_list.cc
index 902ba39e2d72..a4268fb9dc24 100644
--- a/cobalt/csp/source_list.cc
+++ b/cobalt/csp/source_list.cc
@@ -35,7 +35,7 @@ bool IsSourceListNone(const char* begin, const char* end) {
   const char* position = begin;
   SkipWhile<IsSourceCharacter>(&position, end);
   size_t len = static_cast<size_t>(position - begin);
-  if (base::strncasecmp("'none'", begin, len) != 0) {
+  if (strncasecmp("'none'", begin, len) != 0) {
     return false;
   }
 
@@ -400,7 +400,7 @@ bool SourceList::ParseNonce(const char* begin, const char* end,
   const char* prefix = "'nonce-";
 
   if (nonce_length <= strlen(prefix) ||
-      base::strncasecmp(prefix, begin, strlen(prefix)) != 0) {
+      strncasecmp(prefix, begin, strlen(prefix)) != 0) {
     return true;
   }
 
@@ -433,8 +433,7 @@ bool SourceList::ParseHash(const char* begin, const char* end,
   for (size_t i = 0; i < arraysize(kSupportedPrefixes); ++i) {
     const HashPrefix& algorithm = kSupportedPrefixes[i];
     if (hash_length > strlen(algorithm.prefix) &&
-        base::strncasecmp(algorithm.prefix, begin, strlen(algorithm.prefix)) ==
-            0) {
+        strncasecmp(algorithm.prefix, begin, strlen(algorithm.prefix)) == 0) {
       prefix = algorithm.prefix;
       *hash_algorithm = algorithm.type;
       break;
diff --git a/cobalt/debug/console/command_manager.cc b/cobalt/debug/console/command_manager.cc
index 3c30ae38912e..99a9420c5990 100644
--- a/cobalt/debug/console/command_manager.cc
+++ b/cobalt/debug/console/command_manager.cc
@@ -50,9 +50,9 @@ ConsoleCommandManager::CommandHandler::~CommandHandler() {
 // static
 bool ConsoleCommandManager::CommandHandler::IsOnEnableOrTrue(
     const std::string& message) {
-  return (SbStringCompareNoCase("on", message.c_str()) == 0) ||
-         (SbStringCompareNoCase("enable", message.c_str()) == 0) ||
-         (SbStringCompareNoCase("true", message.c_str()) == 0);
+  return (strcasecmp("on", message.c_str()) == 0) ||
+         (strcasecmp("enable", message.c_str()) == 0) ||
+         (strcasecmp("true", message.c_str()) == 0);
 }
 
 
diff --git a/cobalt/dom/document.cc b/cobalt/dom/document.cc
index e405cd9de197..6fb63cdc46cf 100644
--- a/cobalt/dom/document.cc
+++ b/cobalt/dom/document.cc
@@ -235,26 +235,26 @@ scoped_refptr<web::Event> Document::CreateEvent(
     script::ExceptionState* exception_state) {
   // https://www.w3.org/TR/dom/#dom-document-createevent
   // The match of interface name is case-insensitive.
-  if (base::strcasecmp(interface_name.c_str(), "event") == 0 ||
-      base::strcasecmp(interface_name.c_str(), "events") == 0 ||
-      base::strcasecmp(interface_name.c_str(), "htmlevents") == 0) {
+  if (strcasecmp(interface_name.c_str(), "event") == 0 ||
+      strcasecmp(interface_name.c_str(), "events") == 0 ||
+      strcasecmp(interface_name.c_str(), "htmlevents") == 0) {
     return new web::Event(web::Event::Uninitialized);
-  } else if (base::strcasecmp(interface_name.c_str(), "keyboardevent") == 0 ||
-             base::strcasecmp(interface_name.c_str(), "keyevents") == 0) {
+  } else if (strcasecmp(interface_name.c_str(), "keyboardevent") == 0 ||
+             strcasecmp(interface_name.c_str(), "keyevents") == 0) {
     return new KeyboardEvent(web::Event::Uninitialized);
-  } else if (base::strcasecmp(interface_name.c_str(), "messageevent") == 0) {
+  } else if (strcasecmp(interface_name.c_str(), "messageevent") == 0) {
     return new web::MessageEvent(web::Event::Uninitialized);
-  } else if (base::strcasecmp(interface_name.c_str(), "mouseevent") == 0 ||
-             base::strcasecmp(interface_name.c_str(), "mouseevents") == 0) {
+  } else if (strcasecmp(interface_name.c_str(), "mouseevent") == 0 ||
+             strcasecmp(interface_name.c_str(), "mouseevents") == 0) {
     return new MouseEvent(web::Event::Uninitialized);
-  } else if (base::strcasecmp(interface_name.c_str(), "uievent") == 0 ||
-             base::strcasecmp(interface_name.c_str(), "uievents") == 0) {
+  } else if (strcasecmp(interface_name.c_str(), "uievent") == 0 ||
+             strcasecmp(interface_name.c_str(), "uievents") == 0) {
     return new UIEvent(web::Event::Uninitialized);
-  } else if (base::strcasecmp(interface_name.c_str(), "wheelevent") == 0) {
+  } else if (strcasecmp(interface_name.c_str(), "wheelevent") == 0) {
     // This not in the spec, but commonly implemented to create a WheelEvent.
     //   https://www.w3.org/TR/2016/WD-uievents-20160804/#interface-wheelevent
     return new WheelEvent(web::Event::Uninitialized);
-  } else if (base::strcasecmp(interface_name.c_str(), "customevent") == 0) {
+  } else if (strcasecmp(interface_name.c_str(), "customevent") == 0) {
     return new web::CustomEvent(web::Event::Uninitialized);
   }
 
diff --git a/cobalt/dom/html_media_element.cc b/cobalt/dom/html_media_element.cc
index da10b2e91781..dfbfa2a9de66 100644
--- a/cobalt/dom/html_media_element.cc
+++ b/cobalt/dom/html_media_element.cc
@@ -138,7 +138,7 @@ HTMLMediaElement::HTMLMediaElement(Document* document, base::Token tag_name)
       ready_state_(WebMediaPlayer::kReadyStateHaveNothing),
       ready_state_maximum_(WebMediaPlayer::kReadyStateHaveNothing),
       volume_(1.0f),
-      last_seek_time_(0),
+      last_seek_time_(0.0),
       previous_progress_time_(std::numeric_limits<double>::max()),
       duration_(std::numeric_limits<double>::quiet_NaN()),
       playing_(false),
@@ -149,7 +149,7 @@ HTMLMediaElement::HTMLMediaElement(Document* document, base::Token tag_name)
       resume_frozen_flag_(false),
       seeking_(false),
       controls_(false),
-      last_time_update_event_movie_time_(std::numeric_limits<float>::max()),
+      last_time_update_event_movie_time_(std::numeric_limits<double>::max()),
       processing_media_player_callback_(0),
       media_source_url_(std::string(kMediaSourceUrlProtocol) + ':' +
                         base::GenerateGUID()),
@@ -222,7 +222,7 @@ scoped_refptr<TimeRanges> HTMLMediaElement::buffered() const {
   }
 
   player_->UpdateBufferedTimeRanges(
-      [&](float start, float end) { buffered->Add(start, end); });
+      [&](double start, double end) { buffered->Add(start, end); });
   return buffered;
 }
 
@@ -344,11 +344,11 @@ bool HTMLMediaElement::seeking() const {
   return seeking_;
 }
 
-float HTMLMediaElement::current_time(
+double HTMLMediaElement::current_time(
     script::ExceptionState* exception_state) const {
   if (!player_) {
     LOG(INFO) << 0 << " (because player is NULL)";
-    return 0;
+    return 0.0;
   }
 
   if (seeking_) {
@@ -356,15 +356,14 @@ float HTMLMediaElement::current_time(
     return last_seek_time_;
   }
 
-  float time = player_->GetCurrentTime();
+  const double time = player_->GetCurrentTime();
   MLOG() << time << " (from player)";
   return time;
 }
 
 void HTMLMediaElement::set_current_time(
-    float time, script::ExceptionState* exception_state) {
+    double time, script::ExceptionState* exception_state) {
   // 4.8.9.9 Seeking
-
   // 1 - If the media element's readyState is
   // WebMediaPlayer::kReadyStateHaveNothing, then raise an INVALID_STATE_ERR
   // exception.
@@ -377,10 +376,9 @@ void HTMLMediaElement::set_current_time(
   Seek(time);
 }
 
-float HTMLMediaElement::duration() const {
+double HTMLMediaElement::duration() const {
   MLOG() << duration_;
-  // TODO: Turn duration into double.
-  return static_cast<float>(duration_);
+  return duration_;
 }
 
 base::Time HTMLMediaElement::GetStartDate() const {
@@ -433,7 +431,7 @@ void HTMLMediaElement::set_playback_rate(float rate) {
 const scoped_refptr<TimeRanges>& HTMLMediaElement::played() {
   MLOG();
   if (playing_) {
-    float time = current_time(NULL);
+    const double time = current_time(NULL);
     if (time > last_seek_time_) {
       AddPlayedRange(last_seek_time_, time);
     }
@@ -447,8 +445,8 @@ const scoped_refptr<TimeRanges>& HTMLMediaElement::played() {
 }
 
 scoped_refptr<TimeRanges> HTMLMediaElement::seekable() const {
-  if (player_ && player_->GetMaxTimeSeekable() != 0) {
-    double max_time_seekable = player_->GetMaxTimeSeekable();
+  if (player_ && player_->GetMaxTimeSeekable() != 0.0) {
+    const double max_time_seekable = player_->GetMaxTimeSeekable();
     MLOG() << "(0, " << max_time_seekable << ")";
     return new TimeRanges(0, max_time_seekable);
   }
@@ -632,7 +630,7 @@ void HTMLMediaElement::DurationChanged(double duration, bool request_seek) {
   ScheduleOwnEvent(base::Tokens::durationchange());
 
   if (request_seek) {
-    Seek(static_cast<float>(duration));
+    Seek(duration);
   }
 }
 
@@ -775,7 +773,7 @@ void HTMLMediaElement::PrepareForLoad() {
 
   // 2 - Asynchronously await a stable state.
   played_time_ranges_ = new TimeRanges;
-  last_seek_time_ = 0;
+  last_seek_time_ = 0.0;
 
   ConfigureMediaControls();
 }
@@ -1019,8 +1017,8 @@ void HTMLMediaElement::OnProgressEventTimer() {
     return;
   }
 
-  double time = base::Time::Now().ToDoubleT();
-  double time_delta = time - previous_progress_time_;
+  const double time = base::Time::Now().ToDoubleT();
+  const double time_delta = time - previous_progress_time_;
 
   if (player_->DidLoadingProgress()) {
     ScheduleOwnEvent(base::Tokens::progress());
@@ -1082,7 +1080,7 @@ void HTMLMediaElement::StopPeriodicTimers() {
 void HTMLMediaElement::ScheduleTimeupdateEvent(bool periodic_event) {
   // Some media engines make multiple "time changed" callbacks at the same time,
   // but we only want one event at a given time so filter here
-  float movie_time = current_time(NULL);
+  const double movie_time = current_time(NULL);
   if (movie_time != last_time_update_event_movie_time_) {
     if (!periodic_event && playback_progress_timer_.IsRunning()) {
       playback_progress_timer_.Reset();
@@ -1268,7 +1266,7 @@ void HTMLMediaElement::ChangeNetworkStateFromLoadingToIdle() {
   network_state_ = kNetworkIdle;
 }
 
-void HTMLMediaElement::Seek(float time) {
+void HTMLMediaElement::Seek(double time) {
   LOG(INFO) << "Seek to " << time << ".";
   // 4.8.9.9 Seeking - continued from set_current_time().
 
@@ -1279,7 +1277,7 @@ void HTMLMediaElement::Seek(float time) {
 
   // Get the current time before setting seeking_, last_seek_time_ is returned
   // once it is set.
-  float now = current_time(NULL);
+  const double now = current_time(NULL);
 
   // 2 - If the element's seeking IDL attribute is true, then another instance
   // of this algorithm is already running. Abort that other instance of the
@@ -1297,7 +1295,7 @@ void HTMLMediaElement::Seek(float time) {
 
   // 6 - If the new playback position is less than the earliest possible
   // position, let it be that position instead.
-  time = std::max(time, 0.f);
+  time = std::max(time, 0.0);
 
   // 7 - If the (possibly now changed) new playback position is not in one of
   // the ranges given in the seekable attribute, then let it be the position in
@@ -1329,7 +1327,7 @@ void HTMLMediaElement::Seek(float time) {
     seeking_ = false;
     return;
   }
-  time = static_cast<float>(seekable_ranges->Nearest(time));
+  time = seekable_ranges->Nearest(time);
 
   if (playing_) {
     if (last_seek_time_ < now) {
@@ -1361,7 +1359,7 @@ void HTMLMediaElement::FinishSeek() {
   ScheduleOwnEvent(base::Tokens::seeked());
 }
 
-void HTMLMediaElement::AddPlayedRange(float start, float end) {
+void HTMLMediaElement::AddPlayedRange(double start, double end) {
   if (!played_time_ranges_) {
     played_time_ranges_ = new TimeRanges;
   }
@@ -1411,7 +1409,7 @@ void HTMLMediaElement::UpdatePlayState() {
 
     playback_progress_timer_.Stop();
     playing_ = false;
-    float time = current_time(NULL);
+    const double time = current_time(NULL);
     if (time > last_seek_time_) {
       AddPlayedRange(last_seek_time_, time);
     }
@@ -1431,7 +1429,7 @@ bool HTMLMediaElement::PotentiallyPlaying() const {
 }
 
 bool HTMLMediaElement::EndedPlayback() const {
-  float dur = duration();
+  const double dur = duration();
   if (!player_ || std::isnan(dur)) {
     return false;
   }
@@ -1448,15 +1446,15 @@ bool HTMLMediaElement::EndedPlayback() const {
   // direction of playback is forwards, Either the media element does not have a
   // loop attribute specified, or the media element has a current media
   // controller.
-  float now = current_time(NULL);
-  if (playback_rate_ > 0) {
-    return dur > 0 && now >= dur && !loop();
+  const double now = current_time(NULL);
+  if (playback_rate_ > 0.f) {
+    return dur > 0.0 && now >= dur && !loop();
   }
 
   // or the current playback position is the earliest possible position and the
   // direction of playback is backwards
-  if (playback_rate_ < 0) {
-    return now <= 0;
+  if (playback_rate_ < 0.f) {
+    return now <= 0.0;
   }
 
   return false;
@@ -1557,14 +1555,14 @@ void HTMLMediaElement::TimeChanged(bool eos_played) {
   // already posted one at the current movie time.
   ScheduleTimeupdateEvent(false);
 
-  float now = current_time(NULL);
-  float dur = duration();
+  const double now = current_time(NULL);
+  const double dur = duration();
 
   // When the current playback position reaches the end of the media resource
   // when the direction of playback is forwards, then the user agent must follow
   // these steps:
   eos_played |=
-      !std::isnan(dur) && (0.0f != dur) && now >= dur && playback_rate_ > 0;
+      !std::isnan(dur) && (0.0 != dur) && now >= dur && playback_rate_ > 0.f;
   if (eos_played) {
     LOG(INFO) << "End of stream is played.";
     // If the media element has a loop attribute specified and does not have a
@@ -1573,7 +1571,7 @@ void HTMLMediaElement::TimeChanged(bool eos_played) {
       sent_end_event_ = false;
       // then seek to the earliest possible position of the media resource and
       // abort these steps.
-      Seek(0);
+      Seek(0.0);
     } else {
       // If the media element does not have a current media controller, and the
       // media element has still ended playback, and the direction of playback
@@ -1603,7 +1601,7 @@ void HTMLMediaElement::DurationChanged() {
 
   ScheduleOwnEvent(base::Tokens::durationchange());
 
-  double now = current_time(NULL);
+  const double now = current_time(NULL);
   // Reset and update |duration_|.
   duration_ = std::numeric_limits<double>::quiet_NaN();
   if (player_ && ready_state_ >= WebMediaPlayer::kReadyStateHaveMetadata) {
@@ -1611,7 +1609,7 @@ void HTMLMediaElement::DurationChanged() {
   }
 
   if (now > duration_) {
-    Seek(static_cast<float>(duration_));
+    Seek(duration_);
   }
 
   EndProcessingMediaPlayerCallback();
diff --git a/cobalt/dom/html_media_element.h b/cobalt/dom/html_media_element.h
index 612e21cf20bc..db05a0cd7356 100644
--- a/cobalt/dom/html_media_element.h
+++ b/cobalt/dom/html_media_element.h
@@ -105,9 +105,9 @@ class HTMLMediaElement : public HTMLElement,
   bool seeking() const;
 
   // Playback state
-  float current_time(script::ExceptionState* exception_state) const;
-  void set_current_time(float time, script::ExceptionState* exception_state);
-  float duration() const;
+  double current_time(script::ExceptionState* exception_state) const;
+  void set_current_time(double time, script::ExceptionState* exception_state);
+  double duration() const;
   base::Time GetStartDate() const;
   bool paused() const;
   bool resume_frozen_flag() const;
@@ -210,10 +210,10 @@ class HTMLMediaElement : public HTMLElement,
   void ChangeNetworkStateFromLoadingToIdle();
 
   // Playback
-  void Seek(float time);
+  void Seek(double time);
   void FinishSeek();
 
-  void AddPlayedRange(float start, float end);
+  void AddPlayedRange(double start, double end);
 
   void UpdateVolume();
   void UpdatePlayState();
@@ -269,7 +269,7 @@ class HTMLMediaElement : public HTMLElement,
   WebMediaPlayer::ReadyState ready_state_maximum_;
 
   float volume_;
-  float last_seek_time_;
+  double last_seek_time_;
   double previous_progress_time_;
 
   double duration_;
diff --git a/cobalt/dom/on_screen_keyboard.cc b/cobalt/dom/on_screen_keyboard.cc
index ec41ff409b62..74fbe8315e16 100644
--- a/cobalt/dom/on_screen_keyboard.cc
+++ b/cobalt/dom/on_screen_keyboard.cc
@@ -51,8 +51,7 @@ bool ParseColor(const char* color_str, int& r, int& g, int& b) {
   }
 
   // Handle rgb color notation rgb(R, G, B)
-  if (!is_hex && len >= 10 &&
-      SbStringCompareNoCaseN("rgb(", color_str, 4) == 0) {
+  if (!is_hex && len >= 10 && strncasecmp("rgb(", color_str, 4) == 0) {
     int rgb_tmp[3] = {-1, -1, -1};
     const char* ptr = color_str + 4;
     int i = 0;
diff --git a/cobalt/h5vcc/h5vcc_settings.cc b/cobalt/h5vcc/h5vcc_settings.cc
index 4c47039c28d5..59d76c863024 100644
--- a/cobalt/h5vcc/h5vcc_settings.cc
+++ b/cobalt/h5vcc/h5vcc_settings.cc
@@ -104,5 +104,22 @@ bool H5vccSettings::Set(const std::string& name, SetValueType value) const {
   return false;
 }
 
+void H5vccSettings::SetPersistentSettingAsInt(const std::string& key,
+                                              int value) const {
+  if (persistent_settings_) {
+    persistent_settings_->SetPersistentSetting(
+        key, std::make_unique<base::Value>(value));
+  }
+}
+
+int H5vccSettings::GetPersistentSettingAsInt(const std::string& key,
+                                             int default_setting) const {
+  if (persistent_settings_) {
+    return persistent_settings_->GetPersistentSettingAsInt(key,
+                                                           default_setting);
+  }
+  return default_setting;
+}
+
 }  // namespace h5vcc
 }  // namespace cobalt
diff --git a/cobalt/h5vcc/h5vcc_settings.h b/cobalt/h5vcc/h5vcc_settings.h
index f7e10cf56de4..d958c724e800 100644
--- a/cobalt/h5vcc/h5vcc_settings.h
+++ b/cobalt/h5vcc/h5vcc_settings.h
@@ -58,6 +58,11 @@ class H5vccSettings : public script::Wrappable {
   // invalid or not set to the expected value.
   bool Set(const std::string& name, SetValueType value) const;
 
+  void SetPersistentSettingAsInt(const std::string& key, int value) const;
+
+  int GetPersistentSettingAsInt(const std::string& key,
+                                int default_setting) const;
+
   DEFINE_WRAPPABLE_TYPE(H5vccSettings);
 
  private:
diff --git a/cobalt/h5vcc/h5vcc_settings.idl b/cobalt/h5vcc/h5vcc_settings.idl
index 34650a9d1f63..703e483897c4 100644
--- a/cobalt/h5vcc/h5vcc_settings.idl
+++ b/cobalt/h5vcc/h5vcc_settings.idl
@@ -14,4 +14,6 @@
 
 interface H5vccSettings {
   boolean set(DOMString name, (long or DOMString) value);
+  void setPersistentSettingAsInt(DOMString name, long value);
+  long getPersistentSettingAsInt(DOMString name, long default_setting);
 };
diff --git a/cobalt/loader/cors_preflight.cc b/cobalt/loader/cors_preflight.cc
index 980f4d971f1b..d0750b166d2c 100644
--- a/cobalt/loader/cors_preflight.cc
+++ b/cobalt/loader/cors_preflight.cc
@@ -117,7 +117,7 @@ bool IsInArray(const char* input_str, const char* array[], size_t size) {
     return false;
   }
   for (size_t i = 0; i < size; ++i) {
-    if (SbStringCompareNoCase(input_str, array[i]) == 0) {
+    if (strcasecmp(input_str, array[i]) == 0) {
       return true;
     }
   }
@@ -132,8 +132,7 @@ bool HasFieldValue(const std::vector<std::string>& field_values,
     if (field_values[i].empty()) {
       continue;
     }
-    if (SbStringCompareNoCase(field_values[i].c_str(),
-                              find_value_name.c_str()) == 0) {
+    if (strcasecmp(field_values[i].c_str(), find_value_name.c_str()) == 0) {
       return true;
     }
   }
@@ -171,7 +170,7 @@ bool CORSPreflight::IsSafeRequestHeader(const std::string& name,
 
   // Safe if header name is 'Content-Type' and value is a match of
   // kAllowedMIMEType.
-  if (SbStringCompareNoCase(name.c_str(), kContentType) == 0) {
+  if (strcasecmp(name.c_str(), kContentType) == 0) {
     std::vector<std::string> content_type_split = base::SplitString(
         value, ";", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
     auto begin_iter = content_type_split[0].cbegin();
@@ -220,8 +219,8 @@ bool CORSPreflight::IsSafeResponseHeader(
   }
 
   for (size_t i = 0; i < CORS_exposed_header_name_list.size(); i++) {
-    if (SbStringCompareNoCase(CORS_exposed_header_name_list.at(i).c_str(),
-                              name.c_str()) == 0) {
+    if (strcasecmp(CORS_exposed_header_name_list.at(i).c_str(), name.c_str()) ==
+        0) {
       return true;
     }
   }
@@ -381,7 +380,7 @@ void CORSPreflight::OnURLFetchComplete(const net::URLFetcher* source) {
       if (HasFieldValue(headernames_vec, it.name())) {
         continue;
       }
-      if (SbStringCompareNoCase(it.name().c_str(), kAuthorization) == 0 ||
+      if (strcasecmp(it.name().c_str(), kAuthorization) == 0 ||
           (!HasFieldValue(headernames_vec, "*") &&
            !IsSafeRequestHeader(it.name(), it.value()))) {
         error_callback_.Run();
diff --git a/cobalt/loader/cors_preflight_cache.cc b/cobalt/loader/cors_preflight_cache.cc
index c16d31339679..cd5302d58e0d 100644
--- a/cobalt/loader/cors_preflight_cache.cc
+++ b/cobalt/loader/cors_preflight_cache.cc
@@ -127,7 +127,7 @@ bool CORSPreflightCache::HaveEntry(
   if (entry_ptr->allow_all_headers_except_non_wildcard) {
     bool has_auth_header = false;
     for (const auto& header : unsafe_headernames) {
-      if (SbStringCompareNoCase(header.c_str(), kAuthorization)) {
+      if (strcasecmp(header.c_str(), kAuthorization)) {
         has_auth_header = true;
         break;
       }
diff --git a/cobalt/loader/cors_preflight_cache.h b/cobalt/loader/cors_preflight_cache.h
index 6e063d5b18a2..e1a72bfcc80f 100644
--- a/cobalt/loader/cors_preflight_cache.h
+++ b/cobalt/loader/cors_preflight_cache.h
@@ -54,7 +54,7 @@ class CORSPreflightCache : public base::RefCounted<CORSPreflightCache> {
   // Case-insensitive comparator.
   struct CaseInsensitiveCompare {
     bool operator()(const std::string& lhs, const std::string& rhs) const {
-      return SbStringCompareNoCase(lhs.c_str(), rhs.c_str()) < 0;
+      return strcasecmp(lhs.c_str(), rhs.c_str()) < 0;
     }
   };
 
diff --git a/cobalt/media/player/web_media_player.h b/cobalt/media/player/web_media_player.h
index 459ec6ed0b86..1f8f2646733e 100644
--- a/cobalt/media/player/web_media_player.h
+++ b/cobalt/media/player/web_media_player.h
@@ -41,7 +41,7 @@ class WebMediaPlayer {
   // Return true if the punch through box should be rendered.  Return false if
   // no punch through box should be rendered.
   typedef base::Callback<bool(int x, int y, int width, int height)> SetBoundsCB;
-  typedef std::function<void(float start, float end)> AddRangeCB;
+  typedef std::function<void(double start, double end)> AddRangeCB;
 
   enum NetworkState {
     kNetworkStateEmpty,
@@ -109,12 +109,12 @@ class WebMediaPlayer {
   // Playback controls.
   virtual void Play() = 0;
   virtual void Pause() = 0;
-  virtual void Seek(float seconds) = 0;
+  virtual void Seek(double seconds) = 0;
   virtual void SetRate(float rate) = 0;
   virtual void SetVolume(float volume) = 0;
   virtual void SetVisible(bool visible) = 0;
   virtual void UpdateBufferedTimeRanges(const AddRangeCB& add_range_cb) = 0;
-  virtual float GetMaxTimeSeekable() const = 0;
+  virtual double GetMaxTimeSeekable() const = 0;
 
   // Suspend/Resume
   virtual void Suspend() = 0;
@@ -136,11 +136,11 @@ class WebMediaPlayer {
   // Getters of playback state.
   virtual bool IsPaused() const = 0;
   virtual bool IsSeeking() const = 0;
-  virtual float GetDuration() const = 0;
+  virtual double GetDuration() const = 0;
 #if SB_HAS(PLAYER_WITH_URL)
   virtual base::Time GetStartDate() const = 0;
 #endif  // SB_HAS(PLAYER_WITH_URL)
-  virtual float GetCurrentTime() const = 0;
+  virtual double GetCurrentTime() const = 0;
   virtual float GetPlaybackRate() const = 0;
 
   // Get rate of loading the resource.
@@ -152,7 +152,7 @@ class WebMediaPlayer {
 
   virtual bool DidLoadingProgress() const = 0;
 
-  virtual float MediaTimeForTimeValue(float timeValue) const = 0;
+  virtual double MediaTimeForTimeValue(double timeValue) const = 0;
 
   virtual PlayerStatistics GetStatistics() const = 0;
 
diff --git a/cobalt/media/player/web_media_player_impl.cc b/cobalt/media/player/web_media_player_impl.cc
index 6941c04d3d83..48218c90d160 100644
--- a/cobalt/media/player/web_media_player_impl.cc
+++ b/cobalt/media/player/web_media_player_impl.cc
@@ -69,12 +69,12 @@ const char* kMediaEme = "Media.EME.";
 // end of stream position when the current playback position is also near the
 // end of the stream. In this case, "near the end of stream" means "position
 // greater than or equal to duration() - kEndOfStreamEpsilonInSeconds".
-const double kEndOfStreamEpsilonInSeconds = 2.;
+const double kEndOfStreamEpsilonInSeconds = 2.0;
 
 DECLARE_INSTANCE_COUNTER(WebMediaPlayerImpl);
 
 bool IsNearTheEndOfStream(const WebMediaPlayerImpl* wmpi, double position) {
-  float duration = wmpi->GetDuration();
+  const double duration = wmpi->GetDuration();
   if (std::isfinite(duration)) {
     // If video is very short, we always treat a position as near the end.
     if (duration <= kEndOfStreamEpsilonInSeconds) return true;
@@ -84,19 +84,9 @@ bool IsNearTheEndOfStream(const WebMediaPlayerImpl* wmpi, double position) {
 }
 #endif  // defined(COBALT_SKIP_SEEK_REQUEST_NEAR_END)
 
-base::TimeDelta ConvertSecondsToTimestamp(float seconds) {
-  float microseconds = seconds * base::Time::kMicrosecondsPerSecond;
-  float integer = ceilf(microseconds);
-  float difference = integer - microseconds;
-
-  // Round down if difference is large enough.
-  if ((microseconds > 0 && difference > 0.5f) ||
-      (microseconds <= 0 && difference >= 0.5f)) {
-    integer -= 1.0f;
-  }
-
-  // Now we can safely cast to int64 microseconds.
-  return base::TimeDelta::FromMicroseconds(static_cast<int64>(integer));
+base::TimeDelta ConvertSecondsToTimestamp(double seconds) {
+  return base::TimeDelta::FromMicrosecondsD(std::round(
+      seconds * static_cast<double>(base::Time::kMicrosecondsPerSecond)));
 }
 
 }  // namespace
@@ -340,7 +330,7 @@ void WebMediaPlayerImpl::Pause() {
   media_log_->AddEvent<::media::MediaLogEvent::kPause>();
 }
 
-void WebMediaPlayerImpl::Seek(float seconds) {
+void WebMediaPlayerImpl::Seek(double seconds) {
   DCHECK_EQ(main_loop_, base::MessageLoop::current());
 
 #if defined(COBALT_SKIP_SEEK_REQUEST_NEAR_END)
@@ -461,20 +451,20 @@ bool WebMediaPlayerImpl::IsSeeking() const {
   return state_.seeking;
 }
 
-float WebMediaPlayerImpl::GetDuration() const {
+double WebMediaPlayerImpl::GetDuration() const {
   DCHECK_EQ(main_loop_, base::MessageLoop::current());
 
   if (ready_state_ == WebMediaPlayer::kReadyStateHaveNothing)
-    return std::numeric_limits<float>::quiet_NaN();
+    return std::numeric_limits<double>::quiet_NaN();
 
   base::TimeDelta duration = pipeline_->GetMediaDuration();
 
   // Return positive infinity if the resource is unbounded.
   // http://www.whatwg.org/specs/web-apps/current-work/multipage/video.html#dom-media-duration
   if (duration == ::media::kInfiniteDuration)
-    return std::numeric_limits<float>::infinity();
+    return std::numeric_limits<double>::infinity();
 
-  return static_cast<float>(duration.InSecondsF());
+  return duration.InSecondsF();
 }
 
 #if SB_HAS(PLAYER_WITH_URL)
@@ -490,10 +480,12 @@ base::Time WebMediaPlayerImpl::GetStartDate() const {
 }
 #endif  // SB_HAS(PLAYER_WITH_URL)
 
-float WebMediaPlayerImpl::GetCurrentTime() const {
+double WebMediaPlayerImpl::GetCurrentTime() const {
   DCHECK_EQ(main_loop_, base::MessageLoop::current());
-  if (state_.paused) return static_cast<float>(state_.paused_time.InSecondsF());
-  return static_cast<float>(pipeline_->GetMediaTime().InSecondsF());
+  if (state_.paused) {
+    return state_.paused_time.InSecondsF();
+  }
+  return pipeline_->GetMediaTime().InSecondsF();
 }
 
 float WebMediaPlayerImpl::GetPlaybackRate() const {
@@ -533,10 +525,9 @@ void WebMediaPlayerImpl::UpdateBufferedTimeRanges(
   }
 }
 
-float WebMediaPlayerImpl::GetMaxTimeSeekable() const {
+double WebMediaPlayerImpl::GetMaxTimeSeekable() const {
   DCHECK_EQ(main_loop_, base::MessageLoop::current());
-
-  return static_cast<float>(pipeline_->GetMediaDuration().InSecondsF());
+  return pipeline_->GetMediaDuration().InSecondsF();
 }
 
 void WebMediaPlayerImpl::Suspend() { pipeline_->Suspend(); }
@@ -554,7 +545,7 @@ bool WebMediaPlayerImpl::DidLoadingProgress() const {
   return pipeline_->DidLoadingProgress();
 }
 
-float WebMediaPlayerImpl::MediaTimeForTimeValue(float timeValue) const {
+double WebMediaPlayerImpl::MediaTimeForTimeValue(double timeValue) const {
   return ConvertSecondsToTimestamp(timeValue).InSecondsF();
 }
 
diff --git a/cobalt/media/player/web_media_player_impl.h b/cobalt/media/player/web_media_player_impl.h
index adb7ed2a577b..ca85f8120a1a 100644
--- a/cobalt/media/player/web_media_player_impl.h
+++ b/cobalt/media/player/web_media_player_impl.h
@@ -131,12 +131,12 @@ class WebMediaPlayerImpl : public WebMediaPlayer,
   // Playback controls.
   void Play() override;
   void Pause() override;
-  void Seek(float seconds) override;
+  void Seek(double seconds) override;
   void SetRate(float rate) override;
   void SetVolume(float volume) override;
   void SetVisible(bool visible) override;
   void UpdateBufferedTimeRanges(const AddRangeCB& add_range_cb) override;
-  float GetMaxTimeSeekable() const override;
+  double GetMaxTimeSeekable() const override;
 
   // Suspend/Resume
   void Suspend() override;
@@ -158,11 +158,11 @@ class WebMediaPlayerImpl : public WebMediaPlayer,
   // Getters of playback state.
   bool IsPaused() const override;
   bool IsSeeking() const override;
-  float GetDuration() const override;
+  double GetDuration() const override;
 #if SB_HAS(PLAYER_WITH_URL)
   base::Time GetStartDate() const override;
 #endif  // SB_HAS(PLAYER_WITH_URL)
-  float GetCurrentTime() const override;
+  double GetCurrentTime() const override;
   float GetPlaybackRate() const override;
 
   // Get rate of loading the resource.
@@ -176,7 +176,7 @@ class WebMediaPlayerImpl : public WebMediaPlayer,
 
   bool DidLoadingProgress() const override;
 
-  float MediaTimeForTimeValue(float timeValue) const override;
+  double MediaTimeForTimeValue(double timeValue) const override;
 
   PlayerStatistics GetStatistics() const override;
 
@@ -264,7 +264,7 @@ class WebMediaPlayerImpl : public WebMediaPlayer,
           seeking(false),
           playback_rate(0.0f),
           pending_seek(false),
-          pending_seek_seconds(0.0f),
+          pending_seek_seconds(0.0),
           starting(false),
           is_progressive(false),
           is_media_source(false) {}
@@ -288,7 +288,7 @@ class WebMediaPlayerImpl : public WebMediaPlayer,
     // Seek gets pending if another seek is in progress. Only last pending seek
     // will have effect.
     bool pending_seek;
-    float pending_seek_seconds;
+    double pending_seek_seconds;
 
     bool starting;
 
diff --git a/cobalt/media/sandbox/format_guesstimator.cc b/cobalt/media/sandbox/format_guesstimator.cc
index 1225b5aec70d..1a571106caeb 100644
--- a/cobalt/media/sandbox/format_guesstimator.cc
+++ b/cobalt/media/sandbox/format_guesstimator.cc
@@ -118,7 +118,7 @@ std::string ExtractCodecs(const std::string& content_type) {
   std::vector<std::string> tokens = ::base::SplitString(
       content_type, ";", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
   for (size_t i = 1; i < tokens.size(); ++i) {
-    if (base::strncasecmp(tokens[i].c_str(), kCodecs, strlen(kCodecs))) {
+    if (strncasecmp(tokens[i].c_str(), kCodecs, strlen(kCodecs))) {
       continue;
     }
     auto codec = tokens[i].substr(strlen("codecs="));
diff --git a/cobalt/media/sandbox/web_media_player_helper.cc b/cobalt/media/sandbox/web_media_player_helper.cc
index c2364a574518..945c1aa4dfa1 100644
--- a/cobalt/media/sandbox/web_media_player_helper.cc
+++ b/cobalt/media/sandbox/web_media_player_helper.cc
@@ -116,7 +116,7 @@ bool WebMediaPlayerHelper::IsPlaybackFinished() const {
   // Use a small epsilon to ensure that the video can finish properly even when
   // the audio and video streams are shorter than the duration specified in the
   // container.
-  return player_->GetCurrentTime() >= player_->GetDuration() - 0.1f;
+  return player_->GetCurrentTime() >= player_->GetDuration() - 0.1;
 }
 
 }  // namespace sandbox
diff --git a/cobalt/media/sandbox/web_media_player_sandbox.cc b/cobalt/media/sandbox/web_media_player_sandbox.cc
index cfa4a2827475..016444d62a1f 100644
--- a/cobalt/media/sandbox/web_media_player_sandbox.cc
+++ b/cobalt/media/sandbox/web_media_player_sandbox.cc
@@ -329,21 +329,21 @@ class Application {
   }
 
   void AppendData(const std::string& id, ScopedFile* file, int64* offset) {
-    const float kLowWaterMarkInSeconds = 5.f;
+    const double kLowWaterMarkInSeconds = 5.0;
     const int64 kMaxBytesToAppend = 1024 * 1024;
     std::vector<uint8_t> buffer(kMaxBytesToAppend);
 
     while (*offset < file->GetSize()) {
       ::media::Ranges<TimeDelta> ranges = chunk_demuxer_->GetBufferedRanges(id);
-      float end_of_buffer =
-          ranges.size() == 0 ? 0.f : ranges.end(ranges.size() - 1).InSecondsF();
+      const double end_of_buffer =
+          ranges.size() == 0 ? 0.0 : ranges.end(ranges.size() - 1).InSecondsF();
       if (end_of_buffer - player_->GetCurrentTime() > kLowWaterMarkInSeconds) {
         break;
       }
       int64 bytes_to_append =
           std::min(kMaxBytesToAppend, file->GetSize() - *offset);
 
-      auto current_time = player_ ? player_->GetCurrentTime() : 0;
+      const double current_time = player_ ? player_->GetCurrentTime() : 0.0;
       auto evicted = chunk_demuxer_->EvictCodedFrames(
           id, base::TimeDelta::FromSecondsD(current_time), bytes_to_append);
       SB_DCHECK(evicted);
diff --git a/cobalt/media_session/media_session_client.cc b/cobalt/media_session/media_session_client.cc
index ab740dead22d..d0640670d866 100644
--- a/cobalt/media_session/media_session_client.cc
+++ b/cobalt/media_session/media_session_client.cc
@@ -58,7 +58,7 @@ void GuessMediaPositionState(MediaSessionState* session_state,
     *guess_player = current_player;
 
     MediaPositionState position_state;
-    float duration = (*guess_player)->GetDuration();
+    const double duration = (*guess_player)->GetDuration();
     if (std::isfinite(duration)) {
       position_state.set_duration(duration);
     } else if (std::isinf(duration)) {
diff --git a/cobalt/renderer/rasterizer/skia/skia/src/ports/SkFontMgr_cobalt.cc b/cobalt/renderer/rasterizer/skia/skia/src/ports/SkFontMgr_cobalt.cc
index b64037dd062d..918d040d83e0 100644
--- a/cobalt/renderer/rasterizer/skia/skia/src/ports/SkFontMgr_cobalt.cc
+++ b/cobalt/renderer/rasterizer/skia/skia/src/ports/SkFontMgr_cobalt.cc
@@ -307,7 +307,7 @@ void SkFontMgr_Cobalt::LoadLocaleDefault() {
   std::string script =
       icu::Locale::createCanonical(base::GetSystemLanguageScript().c_str())
           .getScript();
-  if (SbStringCompareNoCase(script.c_str(), ROBOTO_SCRIPT) == 0) {
+  if (strcasecmp(script.c_str(), ROBOTO_SCRIPT) == 0) {
     return;
   }
 
@@ -515,7 +515,7 @@ bool SkFontMgr_Cobalt::CheckIfFamilyMatchesLocaleScript(
   }
   std::string family_script =
       icu::Locale::createCanonical(family_tag.c_str()).getScript();
-  if (SbStringCompareNoCase(script, family_script.c_str()) != 0) {
+  if (strcasecmp(script, family_script.c_str()) != 0) {
     return false;
   }
 
diff --git a/cobalt/renderer/rasterizer/skia/skia/src/ports/SkFontStyleSet_cobalt.cc b/cobalt/renderer/rasterizer/skia/skia/src/ports/SkFontStyleSet_cobalt.cc
index 136b2e31bce3..660b96385e80 100644
--- a/cobalt/renderer/rasterizer/skia/skia/src/ports/SkFontStyleSet_cobalt.cc
+++ b/cobalt/renderer/rasterizer/skia/skia/src/ports/SkFontStyleSet_cobalt.cc
@@ -233,12 +233,12 @@ SkFontStyleSet_Cobalt::SkFontStyleSet_Cobalt(
 
     // Only add font formats that match the format setting.
     if (font_format_setting == kTtf) {
-      if (SbStringCompareNoCase("ttf", extension) != 0 &&
-          SbStringCompareNoCase(extension, "ttc") != 0) {
+      if (strcasecmp("ttf", extension) != 0 &&
+          strcasecmp(extension, "ttc") != 0) {
         continue;
       }
     } else if (font_format_setting == kWoff2 &&
-               SbStringCompareNoCase("woff2", extension) != 0) {
+               strcasecmp("woff2", extension) != 0) {
       continue;
     }
 
@@ -273,10 +273,10 @@ SkFontStyleSet_Cobalt::SkFontStyleSet_Cobalt(
     if (index != nullptr) {
       // If style with name already exists in family, replace it.
       if (font_format_setting == kTtfPreferred &&
-          SbStringCompareNoCase("ttf", extension) == 0) {
+          strcasecmp("ttf", extension) == 0) {
         styles_[*index].reset(font);
       } else if (font_format_setting == kWoff2Preferred &&
-                 SbStringCompareNoCase("woff2", extension) == 0) {
+                 strcasecmp("woff2", extension) == 0) {
         styles_[*index].reset(font);
       }
     } else {
diff --git a/cobalt/web/BUILD.gn b/cobalt/web/BUILD.gn
index 042f25581fe5..bbdac0de617f 100644
--- a/cobalt/web/BUILD.gn
+++ b/cobalt/web/BUILD.gn
@@ -185,6 +185,7 @@ target(gtest_target_type, "web_test") {
     "event_target_test.cc",
     "event_test.cc",
     "message_event_test.cc",
+    "message_port_test.cc",
     "url_test.cc",
     "url_utils_test.cc",
     "window_timers_test.cc",
diff --git a/cobalt/web/event_target.cc b/cobalt/web/event_target.cc
index 2622b4b402fb..4d2fc0a61da2 100644
--- a/cobalt/web/event_target.cc
+++ b/cobalt/web/event_target.cc
@@ -282,9 +282,22 @@ void EventTarget::TraceMembers(script::Tracer* tracer) {
   // instead.
 }
 
+void EventTarget::AddEventListenerRegistrationCallback(
+    void* object, base::Token token, base::OnceClosure callback) {
+  base::AutoLock lock(event_listener_registration_mutex_);
+  event_listener_registration_callbacks_[token][object] = std::move(callback);
+}
+
+void EventTarget::RemoveEventListenerRegistrationCallbacks(void* object) {
+  base::AutoLock lock(event_listener_registration_mutex_);
+  for (auto& token : event_listener_registration_callbacks_)
+    token.second.erase(object);
+}
+
 void EventTarget::AddEventListenerInternal(
     std::unique_ptr<EventTargetListenerInfo> listener_info) {
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
+  DCHECK(listener_info);
 
   // Remove existing attribute listener of the same type.
   if (listener_info->is_attribute()) {
@@ -314,7 +327,21 @@ void EventTarget::AddEventListenerInternal(
   debugger_hooks().AsyncTaskScheduled(
       listener_info->task(), listener_info->type().c_str(),
       base::DebuggerHooks::AsyncTaskFrequency::kRecurring);
+
+  base::Token type = listener_info->type();
   event_listener_infos_.push_back(std::move(listener_info));
+
+  {
+    // Call the event listener registration callback.
+    base::AutoLock lock(event_listener_registration_mutex_);
+    auto callbacks = event_listener_registration_callbacks_.find(type);
+    if (callbacks != event_listener_registration_callbacks_.end()) {
+      for (auto& object : callbacks->second) {
+        std::move(object.second).Run();
+      }
+      event_listener_registration_callbacks_.erase(type);
+    }
+  }
 }
 
 bool EventTarget::HasEventListener(base::Token type) {
diff --git a/cobalt/web/event_target.h b/cobalt/web/event_target.h
index 1663f80f0422..f61ae4191b98 100644
--- a/cobalt/web/event_target.h
+++ b/cobalt/web/event_target.h
@@ -15,6 +15,7 @@
 #ifndef COBALT_WEB_EVENT_TARGET_H_
 #define COBALT_WEB_EVENT_TARGET_H_
 
+#include <map>
 #include <memory>
 #include <set>
 #include <string>
@@ -536,7 +537,6 @@ class EventTarget : public script::Wrappable,
   web::EnvironmentSettings* environment_settings() const {
     return environment_settings_;
   }
-
   std::set<base::Token>& event_listener_event_types() const {
     static std::set<base::Token> event_listener_event_types;
     for (auto& event_listener_info : event_listener_infos_) {
@@ -545,6 +545,12 @@ class EventTarget : public script::Wrappable,
     return event_listener_event_types;
   }
 
+  // Register a callback to be called when an event listener is added for the
+  // given type.
+  void AddEventListenerRegistrationCallback(void* object, base::Token type,
+                                            base::OnceClosure callback);
+  void RemoveEventListenerRegistrationCallbacks(void* object);
+
  protected:
   virtual ~EventTarget() { environment_settings_ = nullptr; }
 
@@ -569,8 +575,12 @@ class EventTarget : public script::Wrappable,
   // the special case of window.onerror handling.
   bool unpack_onerror_events_;
 
-  // Thread checker ensures all calls to the EventTarget are made from the same
-  // thread that it is created in.
+  base::Lock event_listener_registration_mutex_;
+  std::map<base::Token, std::map<void*, base::OnceClosure>>
+      event_listener_registration_callbacks_;
+
+  // Thread checker ensures all calls to the EventTarget are made from the
+  // same thread that it is created in.
   THREAD_CHECKER(thread_checker_);
 };
 
diff --git a/cobalt/web/message_port.cc b/cobalt/web/message_port.cc
index 871874b208d7..f6de8e2c998c 100644
--- a/cobalt/web/message_port.cc
+++ b/cobalt/web/message_port.cc
@@ -23,7 +23,6 @@
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
-#include "base/message_loop/message_loop.h"
 #include "base/task_runner.h"
 #include "cobalt/script/environment_settings.h"
 #include "cobalt/web/context.h"
@@ -34,31 +33,68 @@
 namespace cobalt {
 namespace web {
 
-MessagePort::MessagePort(web::EventTarget* event_target)
-    : event_target_(event_target) {
-  if (!event_target_) {
-    return;
+void MessagePort::EntangleWithEventTarget(web::EventTarget* event_target) {
+  DCHECK(!event_target_);
+  {
+    base::AutoLock lock(mutex_);
+    event_target_ = event_target;
+    if (!event_target_) {
+      enabled_ = false;
+      return;
+    }
   }
-  Context* context = event_target_->environment_settings()->context();
-  base::MessageLoop* message_loop = context->message_loop();
-  if (!message_loop) {
-    return;
-  }
-  message_loop->task_runner()->PostTask(
+  target_task_runner()->PostTask(
       FROM_HERE,
       base::BindOnce(&Context::AddEnvironmentSettingsChangeObserver,
-                     base::Unretained(context), base::Unretained(this)));
+                     base::Unretained(context()), base::Unretained(this)));
   remove_environment_settings_change_observer_ =
       base::BindOnce(&Context::RemoveEnvironmentSettingsChangeObserver,
-                     base::Unretained(context), base::Unretained(this));
+                     base::Unretained(context()), base::Unretained(this));
+
+  target_task_runner()->PostTask(
+      FROM_HERE,
+      base::Bind(
+          [](MessagePort* message_port,
+             web::EventTarget*
+                 event_target) {  // The first time a MessagePort object's
+                                  // onmessage IDL attribute is set, the
+            // port's port message queue must be enabled, as if the start()
+            // method had been called.
+            //   https://html.spec.whatwg.org/commit-snapshots/465a6b672c703054de278b0f8133eb3ad33d93f4/#messageport
+            if (event_target->HasEventListener(base::Tokens::message())) {
+              message_port->Start();
+            } else {
+              event_target->AddEventListenerRegistrationCallback(
+                  message_port, base::Tokens::message(),
+                  base::BindOnce(&MessagePort::Start,
+                                 base::Unretained(message_port)));
+            }
+          },
+          base::Unretained(this), base::Unretained(event_target)));
 }
 
-MessagePort::~MessagePort() { Close(); }
+void MessagePort::Start() {
+  // The start() method steps are to enable this's port message queue, if it is
+  // not already enabled.
+  //   https://html.spec.whatwg.org/commit-snapshots/465a6b672c703054de278b0f8133eb3ad33d93f4/#dom-messageport-start
+  base::AutoLock lock(mutex_);
+  if (!event_target_) {
+    return;
+  }
+  enabled_ = true;
+  for (auto& message : unshipped_messages_) {
+    PostMessageSerializedLocked(std::move(message));
+  }
+  unshipped_messages_.clear();
+}
 
 void MessagePort::Close() {
+  base::AutoLock lock(mutex_);
+  unshipped_messages_.clear();
   if (!event_target_) {
     return;
   }
+  event_target_->RemoveEventListenerRegistrationCallbacks(this);
   if (remove_environment_settings_change_observer_) {
     std::move(remove_environment_settings_change_observer_).Run();
   }
@@ -66,32 +102,36 @@ void MessagePort::Close() {
 }
 
 void MessagePort::PostMessage(const script::ValueHandleHolder& message) {
-  PostMessageSerialized(std::make_unique<script::StructuredClone>(message));
+  auto structured_clone = std::make_unique<script::StructuredClone>(message);
+  {
+    base::AutoLock lock(mutex_);
+    if (!(event_target_ && enabled_)) {
+      unshipped_messages_.push_back(std::move(structured_clone));
+      return;
+    }
+    PostMessageSerializedLocked(std::move(structured_clone));
+  }
 }
 
-void MessagePort::PostMessageSerialized(
+void MessagePort::PostMessageSerializedLocked(
     std::unique_ptr<script::StructuredClone> structured_clone) {
-  if (!event_target_ || !structured_clone) {
-    return;
-  }
-  // TODO: Forward the location of the origating API call to the PostTask call.
-  base::MessageLoop* message_loop =
-      event_target_->environment_settings()->context()->message_loop();
-  if (!message_loop) {
+  if (!structured_clone || !event_target_ || !enabled_) {
     return;
   }
+  // TODO: Forward the location of the origating API call to the PostTask
+  // call.
   //   https://html.spec.whatwg.org/multipage/workers.html#handler-worker-onmessage
   // TODO: Update MessageEvent to support more types. (b/227665847)
   // TODO: Remove dependency of MessageEvent on net iobuffer (b/227665847)
-  message_loop->task_runner()->PostTask(
-      FROM_HERE, base::BindOnce(&MessagePort::DispatchMessage, AsWeakPtr(),
-                                std::move(structured_clone)));
-}
-
-void MessagePort::DispatchMessage(
-    std::unique_ptr<script::StructuredClone> structured_clone) {
-  event_target_->DispatchEvent(new web::MessageEvent(
-      base::Tokens::message(), std::move(structured_clone)));
+  target_task_runner()->PostTask(
+      FROM_HERE,
+      base::BindOnce(
+          [](base::WeakPtr<web::EventTarget> event_target,
+             std::unique_ptr<script::StructuredClone> structured_clone) {
+            event_target->DispatchEvent(new web::MessageEvent(
+                base::Tokens::message(), std::move(structured_clone)));
+          },
+          event_target_->AsWeakPtr(), std::move(structured_clone)));
 }
 
 }  // namespace web
diff --git a/cobalt/web/message_port.h b/cobalt/web/message_port.h
index cee51093e722..71ef61556a22 100644
--- a/cobalt/web/message_port.h
+++ b/cobalt/web/message_port.h
@@ -17,6 +17,8 @@
 
 #include <memory>
 #include <string>
+#include <utility>
+#include <vector>
 
 #include "base/callback_forward.h"
 #include "base/memory/weak_ptr.h"
@@ -34,14 +36,16 @@ namespace cobalt {
 namespace web {
 
 class MessagePort : public script::Wrappable,
-                    public base::SupportsWeakPtr<MessagePort>,
                     public Context::EnvironmentSettingsChangeObserver {
  public:
-  explicit MessagePort(web::EventTarget* event_target);
-  ~MessagePort();
+  MessagePort() = default;
+  ~MessagePort() { Close(); }
+
   MessagePort(const MessagePort&) = delete;
   MessagePort& operator=(const MessagePort&) = delete;
 
+  void EntangleWithEventTarget(web::EventTarget* event_target);
+
   void OnEnvironmentSettingsChanged(bool context_valid) override {
     if (!context_valid) {
       Close();
@@ -53,10 +57,8 @@ class MessagePort : public script::Wrappable,
   // -> void PostMessage(const script::ValueHandleHolder& message,
   //                     script::Sequence<script::ValueHandle*> transfer) {}
   void PostMessage(const script::ValueHandleHolder& message);
-  void PostMessageSerialized(
-      std::unique_ptr<script::StructuredClone> structured_clone);
 
-  void Start() {}
+  void Start();
   void Close();
 
   const web::EventTargetListenerInfo::EventListenerScriptValue* onmessage()
@@ -91,15 +93,32 @@ class MessagePort : public script::Wrappable,
                                              event_listener);
   }
 
-  web::EventTarget* event_target() { return event_target_; }
+  EventTarget* event_target() const { return event_target_; }
+  Context* context() const {
+    return event_target_ ? event_target_->environment_settings()->context()
+                         : nullptr;
+  }
+  base::TaskRunner* target_task_runner() const {
+    return event_target_ ? event_target_->environment_settings()
+                               ->context()
+                               ->message_loop()
+                               ->task_runner()
+                         : nullptr;
+  }
 
   DEFINE_WRAPPABLE_TYPE(MessagePort);
 
  private:
-  void DispatchMessage(
+  void PostMessageSerializedLocked(
       std::unique_ptr<script::StructuredClone> structured_clone);
 
-  // The event target to dispatch events to.
+  base::Lock mutex_;
+  std::vector<std::unique_ptr<script::StructuredClone>> unshipped_messages_;
+
+  // A port message queue can be enabled or disabled, and is initially disabled.
+  //   https://html.spec.whatwg.org/commit-snapshots/465a6b672c703054de278b0f8133eb3ad33d93f4/#message-ports
+  bool enabled_ = false;
+
   web::EventTarget* event_target_ = nullptr;
   base::OnceClosure remove_environment_settings_change_observer_;
 };
diff --git a/cobalt/web/message_port_test.cc b/cobalt/web/message_port_test.cc
new file mode 100644
index 000000000000..140c2919d053
--- /dev/null
+++ b/cobalt/web/message_port_test.cc
@@ -0,0 +1,45 @@
+// Copyright 2023 The Cobalt Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "cobalt/web/message_port.h"
+
+#include "base/strings/string_util.h"
+#include "cobalt/web/testing/test_with_javascript.h"
+
+
+#define EXPECT_SUBSTRING(needle, haystack) \
+  EXPECT_PRED_FORMAT2(::testing::IsSubstring, (needle), (haystack))
+
+namespace cobalt {
+namespace web {
+
+namespace {
+class MessagePortTestWithJavaScript : public testing::TestWebWithJavaScript {};
+}  // namespace
+
+TEST_P(MessagePortTestWithJavaScript, MessagePortIsNotConstructible) {
+  std::string result;
+  EXPECT_FALSE(EvaluateScript("var event = new MessagePort();", &result))
+      << "Failed to evaluate script.";
+  EXPECT_SUBSTRING("TypeError: MessagePort is not constructible", result)
+      << result;
+}
+
+INSTANTIATE_TEST_CASE_P(
+    MessagePortTestsWithJavaScript, MessagePortTestWithJavaScript,
+    ::testing::ValuesIn(testing::TestWebWithJavaScript::GetWebTypes()),
+    testing::TestWebWithJavaScript::GetTypeName);
+
+}  // namespace web
+}  // namespace cobalt
diff --git a/cobalt/worker/client.cc b/cobalt/worker/client.cc
index 7ca45bec2711..707958867994 100644
--- a/cobalt/worker/client.cc
+++ b/cobalt/worker/client.cc
@@ -22,12 +22,12 @@
 
 namespace cobalt {
 namespace worker {
-Client::Client(web::EnvironmentSettings* client)
-    : MessagePort(client->context()
-                      ->GetWindowOrWorkerGlobalScope()
-                      ->navigator_base()
-                      ->service_worker()) {
+Client::Client(web::EnvironmentSettings* client) {
   DCHECK(client);
+  EntangleWithEventTarget(client->context()
+                              ->GetWindowOrWorkerGlobalScope()
+                              ->navigator_base()
+                              ->service_worker());
   // Algorithm for Create Client:
   //   https://www.w3.org/TR/2022/CRD-service-workers-20220712/#create-client
   // 1. Let clientObject be a new Client object.
diff --git a/cobalt/worker/dedicated_worker.cc b/cobalt/worker/dedicated_worker.cc
index 783cead9bef5..af3e62b5614c 100644
--- a/cobalt/worker/dedicated_worker.cc
+++ b/cobalt/worker/dedicated_worker.cc
@@ -85,7 +85,8 @@ void DedicatedWorker::Initialize(script::ExceptionState* exception_state) {
   // 6. Let worker be a new Worker object.
   // 7. Let outside port be a new MessagePort in outside settings's Realm.
   // 8. Associate the outside port with worker.
-  outside_port_ = new web::MessagePort(this);
+  outside_port_ = new web::MessagePort();
+  outside_port_->EntangleWithEventTarget(this);
   // 9. Run this step in parallel:
   //    1. Run a worker given worker, worker URL, outside settings, outside
   //    port, and options.
diff --git a/cobalt/worker/worker.cc b/cobalt/worker/worker.cc
index 28ee68eefaba..a126d864abac 100644
--- a/cobalt/worker/worker.cc
+++ b/cobalt/worker/worker.cc
@@ -19,7 +19,6 @@
 
 #include "base/location.h"
 #include "base/logging.h"
-#include "base/message_loop/message_loop.h"
 #include "base/task_runner.h"
 #include "base/threading/thread.h"
 #include "cobalt/browser/user_agent_platform_info.h"
@@ -40,6 +39,7 @@ namespace cobalt {
 namespace worker {
 
 Worker::Worker(const char* name, const Options& options) : options_(options) {
+  message_port_ = new web::MessagePort();
   // Algorithm for 'run a worker'
   //   https://html.spec.whatwg.org/commit-snapshots/465a6b672c703054de278b0f8133eb3ad33d93f4/#run-a-worker
   // 1. Let is shared be true if worker is a SharedWorker object, and false
@@ -71,7 +71,6 @@ void Worker::WillDestroyCurrentMessageLoop() {
   // Destroy members that were constructed in the worker thread.
   loader_.reset();
   worker_global_scope_ = nullptr;
-  message_port_ = nullptr;
   content_.reset();
 }
 
@@ -265,7 +264,7 @@ void Worker::Execute(const std::string& content,
   // Done at step 8.
   // 16. Let inside port be a new MessagePort object in inside settings's Realm.
   // 17. Associate inside port with worker global scope.
-  message_port_ = new web::MessagePort(worker_global_scope_);
+  message_port_->EntangleWithEventTarget(worker_global_scope_);
   // 18. Entangle outside port and inside port.
   // TODO(b/226640425): Implement this when Message Ports can be entangled.
   // 19. Create a new WorkerLocation object and associate it with worker global
@@ -280,7 +279,6 @@ void Worker::Execute(const std::string& content,
   //     worker until such time as either the closing flag switches to true or
   //     the worker stops being a suspendable worker.
   // 22. Set inside settings's execution ready flag.
-  execution_ready_.Signal();
   // 23. If script is a classic script, then run the classic script script.
   //     Otherwise, it is a module script; run the module script script.
 
@@ -314,11 +312,11 @@ void Worker::Abort() {
   // Algorithm for 'run a worker'
   //   https://html.spec.whatwg.org/commit-snapshots/465a6b672c703054de278b0f8133eb3ad33d93f4/#run-a-worker
   // 29. Clear the worker global scope's map of active timers.
-  if (worker_global_scope_ && message_loop()) {
-    message_loop()->task_runner()->PostBlockingTask(
+  if (worker_global_scope_ && task_runner()) {
+    task_runner()->PostTask(
         FROM_HERE, base::Bind(
-                       [](WorkerGlobalScope* worker_global_scope) {
-                         worker_global_scope->DestroyTimers();
+                       [](web::WindowOrWorkerGlobalScope* global_scope) {
+                         global_scope->DestroyTimers();
                        },
                        base::Unretained(worker_global_scope_.get())));
   }
@@ -357,20 +355,8 @@ void Worker::Terminate() {
 }
 
 void Worker::PostMessage(const script::ValueHandleHolder& message) {
-  DCHECK(message_loop());
-  auto structured_clone = std::make_unique<script::StructuredClone>(message);
-  if (base::MessageLoop::current() != message_loop()) {
-    // Block until the worker thread is ready to execute code to handle the
-    // event.
-    execution_ready_.Wait();
-    message_loop()->task_runner()->PostTask(
-        FROM_HERE, base::BindOnce(&web::MessagePort::PostMessageSerialized,
-                                  message_port()->AsWeakPtr(),
-                                  std::move(structured_clone)));
-  } else {
-    DCHECK(execution_ready_.IsSignaled());
-    message_port()->PostMessageSerialized(std::move(structured_clone));
-  }
+  DCHECK(message_port_);
+  message_port_->PostMessage(message);
 }
 
 }  // namespace worker
diff --git a/cobalt/worker/worker.h b/cobalt/worker/worker.h
index 364837a2fd01..5cce8cb6514e 100644
--- a/cobalt/worker/worker.h
+++ b/cobalt/worker/worker.h
@@ -24,6 +24,7 @@
 #include "base/memory/scoped_refptr.h"
 #include "base/message_loop/message_loop_current.h"
 #include "base/synchronization/waitable_event.h"
+#include "base/task_runner.h"
 #include "base/threading/thread.h"
 #include "cobalt/base/source_location.h"
 #include "cobalt/csp/content_security_policy.h"
@@ -81,11 +82,9 @@ class Worker : public base::MessageLoop::DestructionObserver {
 
   void Terminate();
 
-  web::MessagePort* message_port() const { return message_port_.get(); }
-
-  // The message loop this object is running on.
-  base::MessageLoop* message_loop() const {
-    return web_agent_ ? web_agent_->message_loop() : nullptr;
+  // The task runner for this object.
+  base::TaskRunner* task_runner() const {
+    return web_agent_ ? web_agent_->message_loop()->task_runner() : nullptr;
   }
 
   void PostMessage(const script::ValueHandleHolder& message);
@@ -138,12 +137,6 @@ class Worker : public base::MessageLoop::DestructionObserver {
 
   // Content of the script. Released after Execute is called.
   std::unique_ptr<std::string> content_;
-
-  // The execution ready flag.
-  //   https://html.spec.whatwg.org/commit-snapshots/465a6b672c703054de278b0f8133eb3ad33d93f4/#concept-environment-execution-ready-flag
-  base::WaitableEvent execution_ready_ = {
-      base::WaitableEvent::ResetPolicy::MANUAL,
-      base::WaitableEvent::InitialState::NOT_SIGNALED};
 };
 
 }  // namespace worker
diff --git a/docker-compose-windows-internal.yml b/docker-compose-windows-internal.yml
index 92482e39ffad..4cea203ad308 100644
--- a/docker-compose-windows-internal.yml
+++ b/docker-compose-windows-internal.yml
@@ -129,28 +129,3 @@ services:
     image: cobalt-kokoro-xb1
     depends_on:
       - xb1
-
-  nxswitch:
-    <<: *common-definitions
-    build:
-      context: ./internal/docker/windows/
-      dockerfile: nxswitch/Dockerfile
-      args:
-        - encoded_keyfile=${ENCODED_GS_SERVICE_KEY_FILE}
-        - FROM_IMAGE=cobalt-build-win-internal
-    environment:
-      <<: *shared-build-env
-      PLATFORM: nxswitch
-    image: cobalt-build-nxswitch
-    depends_on:
-      - cobalt-build-win-internal
-
-  nxswitch-kokoro:
-    build:
-      context: ./internal/docker/windows/kokoro/
-      dockerfile: Dockerfile
-      args:
-        - FROM_IMAGE=${FROM_IMAGE:-cobalt-build-nxswitch}
-    image: cobalt-kokoro-nxswitch
-    depends_on:
-      - nxswitch
diff --git a/starboard/CHANGELOG.md b/starboard/CHANGELOG.md
index afc54a3fe70d..cd8222292d33 100644
--- a/starboard/CHANGELOG.md
+++ b/starboard/CHANGELOG.md
@@ -9,6 +9,12 @@ since the version previous to it.
 
 ## Version 16
 
+### Deprecated SbStringFormat APIs and migrated to POSIX memory APIs
+The StringFormat management APIs `SbStringFormat`, `SbStringFormatF`,
+`SbStringFormatWide`, `SbStringFormatUnsifeF` are deprecated and the
+standard APIs `vsnprintf`, `vfnprintf`, `vswprintf`, `snprintf`
+from `<stdlib.h>` should be used instead.
+
 ### Deprecated SbMemory allocation APIs and migrated to POSIX memory APIs
 The memory management APIs `SbMemoryAllocate`, `SbMemoryReallocate`,
 `SbMemoryCalloc`, `SbMemoryAllocateAligned`, `SbMemoryDeallocate`,
diff --git a/starboard/android/shared/audio_track_audio_sink_type.cc b/starboard/android/shared/audio_track_audio_sink_type.cc
index 438e7d7c7711..dfdf7433f8af 100644
--- a/starboard/android/shared/audio_track_audio_sink_type.cc
+++ b/starboard/android/shared/audio_track_audio_sink_type.cc
@@ -212,8 +212,7 @@ void AudioTrackAudioSink::AudioThreadFunc() {
     if (bridge_.GetAndResetHasAudioDeviceChanged(env)) {
       SB_LOG(INFO) << "Audio device changed, raising a capability changed "
                       "error to restart playback.";
-      ReportError(kSbPlayerErrorCapabilityChanged,
-                  "Audio device capability changed");
+      ReportError(true, "Audio device capability changed");
       break;
     }
 
@@ -317,11 +316,8 @@ void AudioTrackAudioSink::AudioThreadFunc() {
         auto sync_time = start_time_ + accumulated_written_frames *
                                            kSbTimeSecond /
                                            sampling_frequency_hz_;
-        // Not necessary to handle error of WriteData(), even for
-        // kAudioTrackErrorDeadObject, as the audio has reached the end of
-        // stream.
-        // TODO: Ensure that the audio stream can still reach the end when an
-        //       error occurs.
+        // Not necessary to handle error of WriteData(), as the audio has
+        // reached the end of stream.
         WriteData(env, silence_buffer.data(), silence_frames_per_append,
                   sync_time);
       }
@@ -350,16 +346,14 @@ void AudioTrackAudioSink::AudioThreadFunc() {
     SbTime now = SbTimeGetMonotonicNow();
 
     if (written_frames < 0) {
-      // Take all |frames_in_audio_track| as consumed since audio track could be
-      // dead.
-      consume_frames_func_(frames_in_audio_track, now, context_);
-
-      bool capabilities_changed =
-          written_frames == AudioTrackBridge::kAudioTrackErrorDeadObject;
-      ReportError(
-          capabilities_changed,
-          FormatString("Error while writing frames: %d", written_frames));
-      SB_LOG(INFO) << "Restarting playback.";
+      if (written_frames == AudioTrackBridge::kAudioTrackErrorDeadObject) {
+        // There might be an audio device change, try to recreate the player.
+        ReportError(true,
+                    "Failed to write data and received dead object error.");
+      } else {
+        ReportError(false, FormatString("Failed to write data and received %d.",
+                                        written_frames));
+      }
       break;
     } else if (written_frames > 0) {
       last_written_succeeded_at = now;
diff --git a/starboard/android/shared/audio_track_bridge.cc b/starboard/android/shared/audio_track_bridge.cc
index 88494994c1a9..e518f745d83d 100644
--- a/starboard/android/shared/audio_track_bridge.cc
+++ b/starboard/android/shared/audio_track_bridge.cc
@@ -183,13 +183,10 @@ int AudioTrackBridge::WriteSample(const float* samples,
   SB_DCHECK(num_of_samples <= max_samples_per_write_);
 
   num_of_samples = std::min(num_of_samples, max_samples_per_write_);
-
-  // TODO: Test this code path
   env->SetFloatArrayRegion(static_cast<jfloatArray>(j_audio_data_), kNoOffset,
                            num_of_samples, samples);
-  int samples_written = env->CallIntMethodOrAbort(
-      j_audio_track_bridge_, "write", "([FI)I", j_audio_data_, num_of_samples);
-  return samples_written;
+  return env->CallIntMethodOrAbort(j_audio_track_bridge_, "write", "([FI)I",
+                                   j_audio_data_, num_of_samples);
 }
 
 int AudioTrackBridge::WriteSample(const uint16_t* samples,
@@ -201,8 +198,6 @@ int AudioTrackBridge::WriteSample(const uint16_t* samples,
   SB_DCHECK(num_of_samples <= max_samples_per_write_);
 
   num_of_samples = std::min(num_of_samples, max_samples_per_write_);
-
-  // TODO: Test this code path
   env->SetByteArrayRegion(static_cast<jbyteArray>(j_audio_data_), kNoOffset,
                           num_of_samples * sizeof(uint16_t),
                           reinterpret_cast<const jbyte*>(samples));
diff --git a/starboard/android/shared/audio_track_bridge.h b/starboard/android/shared/audio_track_bridge.h
index a5b269684a0a..5d7aeeb8fcd8 100644
--- a/starboard/android/shared/audio_track_bridge.h
+++ b/starboard/android/shared/audio_track_bridge.h
@@ -59,15 +59,18 @@ class AudioTrackBridge {
   void Stop(JniEnvExt* env = JniEnvExt::Get());
   void PauseAndFlush(JniEnvExt* env = JniEnvExt::Get());
 
+  // Returns zero or the positive number of samples written, or a negative error
+  // code.
   int WriteSample(const float* samples,
                   int num_of_samples,
                   JniEnvExt* env = JniEnvExt::Get());
-  // Returns samples written.
   int WriteSample(const uint16_t* samples,
                   int num_of_samples,
                   SbTime sync_time,
                   JniEnvExt* env = JniEnvExt::Get());
   // This is used by passthrough, it treats samples as if they are in bytes.
+  // Returns zero or the positive number of samples written, or a negative error
+  // code.
   int WriteSample(const uint8_t* buffer,
                   int num_of_samples,
                   SbTime sync_time,
diff --git a/starboard/client_porting/poem/strings_poem.h b/starboard/client_porting/poem/strings_poem.h
index 7cab608fb3b2..8cfac86905c7 100644
--- a/starboard/client_porting/poem/strings_poem.h
+++ b/starboard/client_porting/poem/strings_poem.h
@@ -23,11 +23,6 @@
 
 #include "starboard/string.h"
 
-#undef strcasecmp
-#define strcasecmp(s1, s2) SbStringCompareNoCase(s1, s2)
-#undef strncasecmp
-#define strncasecmp(s1, s2) SbStringCompareNoCaseN(s1, s2)
-
 #endif  // POEM_NO_EMULATION
 
 #endif  // STARBOARD
diff --git a/starboard/common/string.h b/starboard/common/string.h
index 975fdf48a908..22f375f5595d 100644
--- a/starboard/common/string.h
+++ b/starboard/common/string.h
@@ -20,7 +20,9 @@
 #define STARBOARD_COMMON_STRING_H_
 
 #include <stdarg.h>
+#if SB_API_VERSION >= 16
 #include <stdio.h>
+#endif
 #include <cstring>
 #include <string>
 #include <vector>
diff --git a/starboard/doc/c99.md b/starboard/doc/c99.md
index e101bcf40f8f..f784f9253772 100644
--- a/starboard/doc/c99.md
+++ b/starboard/doc/c99.md
@@ -131,4 +131,11 @@ deprecated and eventually removed.
 * wmemmove
 * wmemset
 * wcsncmp
+* snprintf
+* sprintf
 * vfwprintf
+* vsnprintf
+* vswprintf
+* ferror
+* fputwc
+* fwide
diff --git a/starboard/elf_loader/exported_symbols.cc b/starboard/elf_loader/exported_symbols.cc
index 9bcf36aed88c..1f8537807bd7 100644
--- a/starboard/elf_loader/exported_symbols.cc
+++ b/starboard/elf_loader/exported_symbols.cc
@@ -404,6 +404,20 @@ ExportedSymbols::ExportedSymbols() {
   REGISTER_SYMBOL(calloc);
   REGISTER_SYMBOL(posix_memalign);
   REGISTER_SYMBOL(free);
+  REGISTER_SYMBOL(sprintf);
+  REGISTER_SYMBOL(snprintf);
+  REGISTER_SYMBOL(vfwprintf);
+  REGISTER_SYMBOL(vsnprintf);
+#if defined(_MSC_VER)
+  // MSVC provides a template with the same name.
+  // The cast helps the compiler to pick the correct C function pointer to be
+  // used.
+  REGISTER_SYMBOL(
+      static_cast<int (*)(wchar_t* buffer, size_t count, const wchar_t* format,
+                          va_list argptr)>(vswprintf));
+#else
+  REGISTER_SYMBOL(vswprintf);
+#endif  // defined(_MSC_VER)
 #endif  // SB_API_VERSION >= 16
 
 }  // NOLINT
diff --git a/starboard/evergreen/testing/run_all_tests.sh b/starboard/evergreen/testing/run_all_tests.sh
index bb9dbb1e8a8d..0894d292654e 100755
--- a/starboard/evergreen/testing/run_all_tests.sh
+++ b/starboard/evergreen/testing/run_all_tests.sh
@@ -24,7 +24,7 @@ AUTH_METHOD="public-key"
 USE_COMPRESSED_SYSTEM_IMAGE="false"
 SYSTEM_IMAGE_EXTENSION=".so"
 
-DISABLE_TESTS="true"
+DISABLE_TESTS="false"
 
 while getopts "d:a:c" o; do
     case "${o}" in
diff --git a/starboard/nplb/string_compare_no_case_n_test.cc b/starboard/nplb/string_compare_no_case_n_test.cc
index 84e422808be4..5cd234978c80 100644
--- a/starboard/nplb/string_compare_no_case_n_test.cc
+++ b/starboard/nplb/string_compare_no_case_n_test.cc
@@ -19,6 +19,7 @@ namespace starboard {
 namespace nplb {
 namespace {
 
+#if SB_API_VERSION < 16
 TEST(SbStringCompareNoCaseNTest, SunnyDaySelf) {
   const char kString[] = "0123456789";
   EXPECT_EQ(0, SbStringCompareNoCaseN(kString, kString, strlen(kString)));
@@ -55,6 +56,7 @@ TEST(SbStringCompareNoCaseNTest, SunnyDayCase) {
   EXPECT_EQ(0,
             SbStringCompareNoCaseN(kString4, kString3, strlen(kString4) / 2));
 }
+#endif  // SB_API_VERSION < 16
 
 }  // namespace
 }  // namespace nplb
diff --git a/starboard/nplb/string_compare_no_case_test.cc b/starboard/nplb/string_compare_no_case_test.cc
index 9d3748092601..73544d0295ca 100644
--- a/starboard/nplb/string_compare_no_case_test.cc
+++ b/starboard/nplb/string_compare_no_case_test.cc
@@ -19,6 +19,7 @@ namespace starboard {
 namespace nplb {
 namespace {
 
+#if SB_API_VERSION < 16
 TEST(SbStringCompareNoCaseTest, SunnyDaySelf) {
   const char kString[] = "0123456789";
   EXPECT_EQ(0, SbStringCompareNoCase(kString, kString));
@@ -36,7 +37,7 @@ TEST(SbStringCompareNoCaseTest, SunnyDayCase) {
   EXPECT_EQ(0, SbStringCompareNoCase(kString1, kString2));
   EXPECT_EQ(0, SbStringCompareNoCase(kString2, kString1));
 }
-
+#endif  // SB_API_VERSION < 16
 }  // namespace
 }  // namespace nplb
 }  // namespace starboard
diff --git a/starboard/nplb/string_format_test.cc b/starboard/nplb/string_format_test.cc
index 3ee33618b623..5e369c9798e5 100644
--- a/starboard/nplb/string_format_test.cc
+++ b/starboard/nplb/string_format_test.cc
@@ -14,6 +14,7 @@
 
 // Here we are not trying to do anything fancy, just to really sanity check that
 // this is hooked up to something.
+#if SB_API_VERSION < 16
 
 #include "starboard/common/string.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -25,7 +26,7 @@ namespace {
 int Format(char* out_buffer, size_t buffer_size, const char* format, ...) {
   va_list arguments;
   va_start(arguments, format);
-  int result = vsnprintf(out_buffer, buffer_size, format, arguments);
+  int result = SbStringFormat(out_buffer, buffer_size, format, arguments);
   va_end(arguments);
   return result;
 }
@@ -45,3 +46,5 @@ TEST(SbStringFormatTest, SunnyDay) {
 }  // namespace
 }  // namespace nplb
 }  // namespace starboard
+
+#endif  // SB_API_VERSION < 16
diff --git a/starboard/nplb/string_format_wide_test.cc b/starboard/nplb/string_format_wide_test.cc
index b51c9c4a9cf9..9487c7e7eaee 100644
--- a/starboard/nplb/string_format_wide_test.cc
+++ b/starboard/nplb/string_format_wide_test.cc
@@ -14,6 +14,7 @@
 
 // Here we are not trying to do anything fancy, just to really sanity check that
 // this is hooked up to something.
+#if SB_API_VERSION < 16
 
 #include "starboard/common/string.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -22,7 +23,6 @@ namespace starboard {
 namespace nplb {
 namespace {
 
-#if SB_API_VERSION <= 15
 int Format(wchar_t* out_buffer,
            size_t buffer_size,
            const wchar_t* format,
@@ -45,8 +45,9 @@ TEST(SbStringFormatWideTest, SunnyDay) {
     EXPECT_EQ(kExpected[i], destination[i]);
   }
 }
-#endif
 
 }  // namespace
 }  // namespace nplb
 }  // namespace starboard
+
+#endif  // SB_API_VERSION < 16
diff --git a/starboard/shared/posix/string_compare_no_case.cc b/starboard/shared/posix/string_compare_no_case.cc
index 4837d888b2a9..79479e7eebe1 100644
--- a/starboard/shared/posix/string_compare_no_case.cc
+++ b/starboard/shared/posix/string_compare_no_case.cc
@@ -17,6 +17,8 @@
 #include <string.h>  // Non-standard, required for some platforms.
 #include <strings.h>
 
+#if SB_API_VERSION < 16
 int SbStringCompareNoCase(const char* string1, const char* string2) {
   return strcasecmp(string1, string2);
 }
+#endif
diff --git a/starboard/shared/posix/string_compare_no_case_n.cc b/starboard/shared/posix/string_compare_no_case_n.cc
index 75c9141a1afb..e56c4fb7ebce 100644
--- a/starboard/shared/posix/string_compare_no_case_n.cc
+++ b/starboard/shared/posix/string_compare_no_case_n.cc
@@ -17,8 +17,10 @@
 #include <string.h>  // Non-standard, required for some platforms.
 #include <strings.h>
 
+#if SB_API_VERSION < 16
 int SbStringCompareNoCaseN(const char* string1,
                            const char* string2,
                            size_t count) {
   return ::strncasecmp(string1, string2, count);
 }
+#endif
diff --git a/starboard/shared/starboard/log_raw_format.cc b/starboard/shared/starboard/log_raw_format.cc
index dc669b5b4309..ee1c99ead81a 100644
--- a/starboard/shared/starboard/log_raw_format.cc
+++ b/starboard/shared/starboard/log_raw_format.cc
@@ -15,9 +15,11 @@
 #include "starboard/common/log.h"
 
 #include <stdarg.h>
+#if SB_API_VERSION >= 16
 #include <stdio.h>
-
+#else
 #include "starboard/common/string.h"
+#endif
 
 void SbLogRawFormat(const char* format, va_list arguments) {
   char message[128];
diff --git a/starboard/shared/starboard/media/mime_type.cc b/starboard/shared/starboard/media/mime_type.cc
index 4954ceeb318e..66d8e4cffa0d 100644
--- a/starboard/shared/starboard/media/mime_type.cc
+++ b/starboard/shared/starboard/media/mime_type.cc
@@ -196,7 +196,7 @@ const std::string& MimeType::GetParamName(int index) const {
 
 int MimeType::GetParamIndexByName(const char* name) const {
   for (size_t i = 0; i < params_.size(); ++i) {
-    if (SbStringCompareNoCase(params_[i].name.c_str(), name) == 0) {
+    if (strcasecmp(params_[i].name.c_str(), name) == 0) {
       return static_cast<int>(i);
     }
   }
diff --git a/starboard/shared/stub/string_compare_no_case.cc b/starboard/shared/stub/string_compare_no_case.cc
index 3434800b2d63..aa767bdb86be 100644
--- a/starboard/shared/stub/string_compare_no_case.cc
+++ b/starboard/shared/stub/string_compare_no_case.cc
@@ -14,6 +14,8 @@
 
 #include "starboard/common/string.h"
 
+#if SB_API_VERSION < 16
 int SbStringCompareNoCase(const char* string1, const char* string2) {
   return 0;
 }
+#endif
diff --git a/starboard/shared/stub/string_compare_no_case_n.cc b/starboard/shared/stub/string_compare_no_case_n.cc
index e04639e26939..aa7ae6323c75 100644
--- a/starboard/shared/stub/string_compare_no_case_n.cc
+++ b/starboard/shared/stub/string_compare_no_case_n.cc
@@ -14,8 +14,10 @@
 
 #include "starboard/common/string.h"
 
+#if SB_API_VERSION < 16
 int SbStringCompareNoCaseN(const char* string1,
                            const char* string2,
                            size_t count) {
   return 0;
 }
+#endif
diff --git a/starboard/shared/stub/string_format.cc b/starboard/shared/stub/string_format.cc
index eb2115f69157..66a996088ceb 100644
--- a/starboard/shared/stub/string_format.cc
+++ b/starboard/shared/stub/string_format.cc
@@ -14,7 +14,7 @@
 
 #include "starboard/common/string.h"
 
-#if SB_API_VERSION <= 15
+#if SB_API_VERSION < 16
 int SbStringFormat(char* out_buffer,
                    size_t buffer_size,
                    const char* format,
diff --git a/starboard/shared/stub/string_format_wide.cc b/starboard/shared/stub/string_format_wide.cc
index 62ddfe780fe4..4bcabdf50d06 100644
--- a/starboard/shared/stub/string_format_wide.cc
+++ b/starboard/shared/stub/string_format_wide.cc
@@ -14,7 +14,7 @@
 
 #include "starboard/common/string.h"
 
-#if SB_API_VERSION <= 15
+#if SB_API_VERSION < 16
 int SbStringFormatWide(wchar_t* out_buffer,
                        size_t buffer_size,
                        const wchar_t* format,
diff --git a/starboard/shared/win32/posix_emu/include/stdlib.h b/starboard/shared/win32/posix_emu/include/stdlib.h
index 7fa9e76d2c8f..8d7c27d98011 100644
--- a/starboard/shared/win32/posix_emu/include/stdlib.h
+++ b/starboard/shared/win32/posix_emu/include/stdlib.h
@@ -17,6 +17,8 @@
 
 // MSVC deprecated strdup() in favor of _strdup()
 #define strdup _strdup
+#define strcasecmp _stricmp
+#define strncasecmp _strnicmp
 
 #if defined(STARBOARD)
 #define free sb_free
diff --git a/starboard/shared/win32/string_compare_no_case.cc b/starboard/shared/win32/string_compare_no_case.cc
index 6021bf7d0ae1..85862f19f9ab 100644
--- a/starboard/shared/win32/string_compare_no_case.cc
+++ b/starboard/shared/win32/string_compare_no_case.cc
@@ -16,6 +16,8 @@
 
 #include <string.h>
 
+#if SB_API_VERSION < 16
 int SbStringCompareNoCase(const char* string1, const char* string2) {
   return _stricmp(string1, string2);
 }
+#endif
diff --git a/starboard/shared/win32/string_compare_no_case_n.cc b/starboard/shared/win32/string_compare_no_case_n.cc
index 7490d3d9c7ce..3ac38d73a953 100644
--- a/starboard/shared/win32/string_compare_no_case_n.cc
+++ b/starboard/shared/win32/string_compare_no_case_n.cc
@@ -16,8 +16,10 @@
 
 #include <string.h>
 
+#if SB_API_VERSION < 16
 int SbStringCompareNoCaseN(const char* string1,
                            const char* string2,
                            size_t count) {
   return _strnicmp(string1, string2, count);
 }
+#endif
diff --git a/starboard/shared/win32/string_format.cc b/starboard/shared/win32/string_format.cc
index 90d5081e4db7..d4dd55b2892a 100644
--- a/starboard/shared/win32/string_format.cc
+++ b/starboard/shared/win32/string_format.cc
@@ -16,11 +16,9 @@
 
 #include <stdio.h>
 
-#if SB_API_VERSION <= 15
 int SbStringFormat(char* out_buffer,
                    size_t buffer_size,
                    const char* format,
                    va_list arguments) {
   return vsnprintf(out_buffer, buffer_size, format, arguments);
 }
-#endif
diff --git a/starboard/shared/win32/string_format_wide.cc b/starboard/shared/win32/string_format_wide.cc
index 30987e179e66..79e8479686b4 100644
--- a/starboard/shared/win32/string_format_wide.cc
+++ b/starboard/shared/win32/string_format_wide.cc
@@ -16,7 +16,7 @@
 
 #include <stdio.h>
 
-#if SB_API_VERSION <= 15
+#if SB_API_VERSION < 16
 int SbStringFormatWide(wchar_t* out_buffer,
                        size_t buffer_size,
                        const wchar_t* format,
diff --git a/starboard/string.h b/starboard/string.h
index ec92ed67788f..d8df5600ac59 100644
--- a/starboard/string.h
+++ b/starboard/string.h
@@ -21,7 +21,7 @@
 
 #include <stdarg.h>
 #include <stdio.h>
-#if SB_API_VERSION <= 15
+#if SB_API_VERSION < 16
 #include <wchar.h>
 #endif
 
@@ -40,7 +40,6 @@ extern "C" {
 //
 // |source|: The string to be copied.
 SB_EXPORT char* SbStringDuplicate(const char* source);
-#endif  // SB_API_VERSION < 16
 
 // Compares two strings, ignoring differences in case. The return value is:
 // - |< 0| if |string1| is ASCII-betically lower than |string2|.
@@ -68,7 +67,6 @@ SB_EXPORT int SbStringCompareNoCaseN(const char* string1,
                                      const char* string2,
                                      size_t count);
 
-#if SB_API_VERSION <= 15
 // Produces a string formatted with |format| and |arguments|, placing as much
 // of the result that will fit into |out_buffer|. The return value specifies
 // the number of characters that the format would produce if |buffer_size| were
@@ -101,7 +99,7 @@ static SB_C_INLINE int SbStringFormatF(char* out_buffer,
                                        ...) {
   va_list arguments;
   va_start(arguments, format);
-  int result = vsnprintf(out_buffer, buffer_size, format, arguments);
+  int result = SbStringFormat(out_buffer, buffer_size, format, arguments);
   va_end(arguments);
   return result;
 }
@@ -120,7 +118,7 @@ static SB_C_INLINE int SbStringFormatUnsafeF(char* out_buffer,
                                              ...) {
   va_list arguments;
   va_start(arguments, format);
-  int result = vsnprintf(out_buffer, SSIZE_MAX, format, arguments);
+  int result = SbStringFormat(out_buffer, SSIZE_MAX, format, arguments);
   va_end(arguments);
   return result;
 }
@@ -151,11 +149,11 @@ static SB_C_INLINE int SbStringFormatWideF(wchar_t* out_buffer,
                                            ...) {
   va_list arguments;
   va_start(arguments, format);
-  int result = vswprintf(out_buffer, buffer_size, format, arguments);
+  int result = SbStringFormatWide(out_buffer, buffer_size, format, arguments);
   va_end(arguments);
   return result;
 }
-#endif
+#endif  // SB_API_VERSION < 16
 
 // Scans |buffer| for |pattern|, placing the extracted values in |arguments|.
 // The return value specifies the number of successfully matched items, which
diff --git a/starboard/stub/platform_configuration/configuration.gni b/starboard/stub/platform_configuration/configuration.gni
index e13b8d3d617b..0283df241a29 100644
--- a/starboard/stub/platform_configuration/configuration.gni
+++ b/starboard/stub/platform_configuration/configuration.gni
@@ -30,5 +30,6 @@ no_pedantic_warnings_config_path =
     "//starboard/stub/platform_configuration:no_pedantic_warnings"
 
 is_clang_16 = true
+assert(!is_host_win, "Stub build is not (yet) supported on windows host")
 
 v8_enable_webassembly = true
diff --git a/starboard/tools/api_leak_detector/api_leak_detector.py b/starboard/tools/api_leak_detector/api_leak_detector.py
index 2dfe7253a698..5a9f3cece51d 100755
--- a/starboard/tools/api_leak_detector/api_leak_detector.py
+++ b/starboard/tools/api_leak_detector/api_leak_detector.py
@@ -94,11 +94,6 @@
     'realloc',
     'strcasecmp',
     'strncasecmp',
-    'vsnprintf',
-    'snprintf',
-    'sprintf',
-    'vswprintf',
-    'vfwprintf',
 ]
 
 
diff --git a/starboard/tools/api_leak_detector/stub/debug/docker_debian10_manifest b/starboard/tools/api_leak_detector/stub/debug/docker_debian10_manifest
index e919919e5367..fe01edfb0e9c 100644
--- a/starboard/tools/api_leak_detector/stub/debug/docker_debian10_manifest
+++ b/starboard/tools/api_leak_detector/stub/debug/docker_debian10_manifest
@@ -104,8 +104,6 @@ putwc
 read
 setlocale
 setvbuf
-snprintf
-sprintf
 stderr
 stdin
 stdout
@@ -115,7 +113,6 @@ strtold_l
 syscall
 ungetc
 ungetwc
-vsnprintf
 vsprintf
 wcrtomb
 wcscmp
diff --git a/starboard/tools/api_leak_detector/stub/debug/gn_built_docker_debian10_manifest b/starboard/tools/api_leak_detector/stub/debug/gn_built_docker_debian10_manifest
index cf6c39d1360d..3c551918852b 100644
--- a/starboard/tools/api_leak_detector/stub/debug/gn_built_docker_debian10_manifest
+++ b/starboard/tools/api_leak_detector/stub/debug/gn_built_docker_debian10_manifest
@@ -105,8 +105,6 @@ putwc
 read
 setlocale
 setvbuf
-snprintf
-sprintf
 stderr
 stdin
 stdout
@@ -116,7 +114,6 @@ strtold_l
 syscall
 ungetc
 ungetwc
-vsnprintf
 vsprintf
 wcrtomb
 wcscmp
diff --git a/starboard/tools/api_leak_detector/stub/debug/manifest b/starboard/tools/api_leak_detector/stub/debug/manifest
index ec8cfb2ec194..c69dcd77c1c7 100644
--- a/starboard/tools/api_leak_detector/stub/debug/manifest
+++ b/starboard/tools/api_leak_detector/stub/debug/manifest
@@ -104,8 +104,6 @@ putwc
 read
 setlocale
 setvbuf
-snprintf
-sprintf
 stderr
 stdin
 stdout
@@ -115,7 +113,6 @@ strtold_l
 syscall
 ungetc
 ungetwc
-vsnprintf
 vsprintf
 wcrtomb
 wcscmp
diff --git a/starboard/tools/api_leak_detector/stub/devel/docker_debian10_manifest b/starboard/tools/api_leak_detector/stub/devel/docker_debian10_manifest
index 514bf719e679..11f332fb8e3e 100644
--- a/starboard/tools/api_leak_detector/stub/devel/docker_debian10_manifest
+++ b/starboard/tools/api_leak_detector/stub/devel/docker_debian10_manifest
@@ -105,8 +105,6 @@ putwc
 read
 setlocale
 setvbuf
-snprintf
-sprintf
 stderr
 stdin
 stdout
@@ -116,7 +114,6 @@ strtold_l
 syscall
 ungetc
 ungetwc
-vsnprintf
 vsprintf
 wcrtomb
 wcscmp
diff --git a/starboard/tools/api_leak_detector/stub/devel/gn_built_docker_debian10_manifest b/starboard/tools/api_leak_detector/stub/devel/gn_built_docker_debian10_manifest
index e7613fc9de70..04eb67b38fde 100644
--- a/starboard/tools/api_leak_detector/stub/devel/gn_built_docker_debian10_manifest
+++ b/starboard/tools/api_leak_detector/stub/devel/gn_built_docker_debian10_manifest
@@ -106,8 +106,6 @@ putwc
 read
 setlocale
 setvbuf
-snprintf
-sprintf
 stderr
 stdin
 stdout
@@ -117,7 +115,6 @@ strtold_l
 syscall
 ungetc
 ungetwc
-vsnprintf
 vsprintf
 wcrtomb
 wcscmp
diff --git a/starboard/tools/api_leak_detector/stub/devel/manifest b/starboard/tools/api_leak_detector/stub/devel/manifest
index bc3b43c1e486..84a89b513bf2 100644
--- a/starboard/tools/api_leak_detector/stub/devel/manifest
+++ b/starboard/tools/api_leak_detector/stub/devel/manifest
@@ -107,8 +107,6 @@ putwc
 read
 setlocale
 setvbuf
-snprintf
-sprintf
 stderr
 stdin
 stdout
@@ -118,7 +116,6 @@ strtold_l
 syscall
 ungetc
 ungetwc
-vsnprintf
 vsprintf
 wcrtomb
 wcscmp
diff --git a/starboard/tools/api_leak_detector/stub/gold/docker_debian10_manifest b/starboard/tools/api_leak_detector/stub/gold/docker_debian10_manifest
index d213db0b3f8c..34f6f5a8f385 100644
--- a/starboard/tools/api_leak_detector/stub/gold/docker_debian10_manifest
+++ b/starboard/tools/api_leak_detector/stub/gold/docker_debian10_manifest
@@ -104,8 +104,6 @@ putwc
 read
 setlocale
 setvbuf
-snprintf
-sprintf
 stderr
 stdin
 stdout
@@ -115,7 +113,6 @@ strtold_l
 syscall
 ungetc
 ungetwc
-vsnprintf
 vsprintf
 wcrtomb
 wcscmp
diff --git a/starboard/tools/api_leak_detector/stub/gold/gn_built_docker_debian10_manifest b/starboard/tools/api_leak_detector/stub/gold/gn_built_docker_debian10_manifest
index 5d95b3a8e714..433d4e1a8386 100644
--- a/starboard/tools/api_leak_detector/stub/gold/gn_built_docker_debian10_manifest
+++ b/starboard/tools/api_leak_detector/stub/gold/gn_built_docker_debian10_manifest
@@ -105,8 +105,6 @@ putwc
 read
 setlocale
 setvbuf
-snprintf
-sprintf
 stderr
 stdin
 stdout
@@ -116,7 +114,6 @@ strtold_l
 syscall
 ungetc
 ungetwc
-vsnprintf
 vsprintf
 wcrtomb
 wcscmp
diff --git a/starboard/tools/api_leak_detector/stub/gold/manifest b/starboard/tools/api_leak_detector/stub/gold/manifest
index 1c368c9befde..2995476c9a88 100644
--- a/starboard/tools/api_leak_detector/stub/gold/manifest
+++ b/starboard/tools/api_leak_detector/stub/gold/manifest
@@ -106,8 +106,6 @@ putwc
 read
 setlocale
 setvbuf
-snprintf
-sprintf
 stderr
 stdin
 stdout
@@ -117,7 +115,6 @@ strtold_l
 syscall
 ungetc
 ungetwc
-vsnprintf
 vsprintf
 wcrtomb
 wcscmp
diff --git a/starboard/tools/api_leak_detector/stub/qa/docker_debian10_manifest b/starboard/tools/api_leak_detector/stub/qa/docker_debian10_manifest
index d213db0b3f8c..34f6f5a8f385 100644
--- a/starboard/tools/api_leak_detector/stub/qa/docker_debian10_manifest
+++ b/starboard/tools/api_leak_detector/stub/qa/docker_debian10_manifest
@@ -104,8 +104,6 @@ putwc
 read
 setlocale
 setvbuf
-snprintf
-sprintf
 stderr
 stdin
 stdout
@@ -115,7 +113,6 @@ strtold_l
 syscall
 ungetc
 ungetwc
-vsnprintf
 vsprintf
 wcrtomb
 wcscmp
diff --git a/starboard/tools/api_leak_detector/stub/qa/gn_built_docker_debian10_manifest b/starboard/tools/api_leak_detector/stub/qa/gn_built_docker_debian10_manifest
index 5d95b3a8e714..433d4e1a8386 100644
--- a/starboard/tools/api_leak_detector/stub/qa/gn_built_docker_debian10_manifest
+++ b/starboard/tools/api_leak_detector/stub/qa/gn_built_docker_debian10_manifest
@@ -105,8 +105,6 @@ putwc
 read
 setlocale
 setvbuf
-snprintf
-sprintf
 stderr
 stdin
 stdout
@@ -116,7 +114,6 @@ strtold_l
 syscall
 ungetc
 ungetwc
-vsnprintf
 vsprintf
 wcrtomb
 wcscmp
diff --git a/starboard/tools/api_leak_detector/stub/qa/manifest b/starboard/tools/api_leak_detector/stub/qa/manifest
index 1c368c9befde..2995476c9a88 100644
--- a/starboard/tools/api_leak_detector/stub/qa/manifest
+++ b/starboard/tools/api_leak_detector/stub/qa/manifest
@@ -106,8 +106,6 @@ putwc
 read
 setlocale
 setvbuf
-snprintf
-sprintf
 stderr
 stdin
 stdout
@@ -117,7 +115,6 @@ strtold_l
 syscall
 ungetc
 ungetwc
-vsnprintf
 vsprintf
 wcrtomb
 wcscmp
diff --git a/third_party/boringssl/src/crypto/mem_starboard.c b/third_party/boringssl/src/crypto/mem_starboard.c
index a0cc626189d9..a9361adc685b 100644
--- a/third_party/boringssl/src/crypto/mem_starboard.c
+++ b/third_party/boringssl/src/crypto/mem_starboard.c
@@ -221,5 +221,9 @@ int BIO_snprintf(char *buf, size_t n, const char *format, ...) {
 }
 
 int BIO_vsnprintf(char *buf, size_t n, const char *format, va_list args) {
+#if SB_API_VERSION < 16
+  return SbStringFormat(buf, n, format, args);
+#else
   return vsnprintf(buf, n, format, args);
+#endif
 }
diff --git a/third_party/chromium/media/base/starboard_utils.cc b/third_party/chromium/media/base/starboard_utils.cc
index 1518fb9abdf9..e7e9e56ec04f 100644
--- a/third_party/chromium/media/base/starboard_utils.cc
+++ b/third_party/chromium/media/base/starboard_utils.cc
@@ -418,7 +418,7 @@ std::string ExtractCodecs(const std::string& mime_type) {
   std::vector<std::string> tokens = ::base::SplitString(
       mime_type, ";", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
   for (size_t i = 1; i < tokens.size(); ++i) {
-    if (base::strncasecmp(tokens[i].c_str(), kCodecs, strlen(kCodecs))) {
+    if (strncasecmp(tokens[i].c_str(), kCodecs, strlen(kCodecs))) {
       continue;
     }
     auto codec = tokens[i].substr(strlen(kCodecs));
diff --git a/third_party/chromium/media/filters/chunk_demuxer.cc b/third_party/chromium/media/filters/chunk_demuxer.cc
index e24189d7fb41..0bb01f4cd5a6 100644
--- a/third_party/chromium/media/filters/chunk_demuxer.cc
+++ b/third_party/chromium/media/filters/chunk_demuxer.cc
@@ -84,7 +84,7 @@ bool ParseMimeType(const std::string& mime_type, std::string* type,
   *type = tokens[0];
   codecs->clear();
   for (size_t i = 1; i < tokens.size(); ++i) {
-    if (base::strncasecmp(tokens[i].c_str(), kCodecs, strlen(kCodecs))) {
+    if (strncasecmp(tokens[i].c_str(), kCodecs, strlen(kCodecs))) {
       continue;
     }
     *codecs = tokens[i].substr(strlen(kCodecs));
diff --git a/third_party/googletest/src/googletest/include/gtest/internal/gtest-port.h b/third_party/googletest/src/googletest/include/gtest/internal/gtest-port.h
index 79d24b24382c..1faa3ca3819b 100644
--- a/third_party/googletest/src/googletest/include/gtest/internal/gtest-port.h
+++ b/third_party/googletest/src/googletest/include/gtest/internal/gtest-port.h
@@ -2085,9 +2085,11 @@ inline int IsATTY(FILE* /*file*/) { return SbLogIsTty() ? 1 : 0; }
 inline int Stat(const char* path, StatStruct* buf) {
   return SbFileGetPathInfo(path, buf) ? 0 : -1;
 }
+#if SB_API_VERSION < 16
 inline int StrCaseCmp(const char* s1, const char* s2) {
   return SbStringCompareNoCase(s1, s2);
 }
+#endif //SB_API_VERSION < 16
 inline char* StrDup(const char* src) { return strdup(src); }
 
 inline int RmDir(const char* dir) { return SbFileDelete(dir); }
diff --git a/third_party/googletest/src/googletest/src/gtest.cc b/third_party/googletest/src/googletest/src/gtest.cc
index 2465a488de53..9ab8d8f04016 100644
--- a/third_party/googletest/src/googletest/src/gtest.cc
+++ b/third_party/googletest/src/googletest/src/gtest.cc
@@ -2133,7 +2133,7 @@ AssertionResult CmpHelperSTRNE(const char* s1_expression,
 bool String::CaseInsensitiveCStringEquals(const char* lhs, const char* rhs) {
   if (lhs == nullptr) return rhs == nullptr;
   if (rhs == nullptr) return false;
-  return posix::StrCaseCmp(lhs, rhs) == 0;
+  return strcasecmp(lhs, rhs) == 0;
 }
 
 // Compares two wide C strings, ignoring case.  Returns true if and only if they
diff --git a/third_party/libvpx/source/libvpx/third_party/googletest/src/src/gtest.cc b/third_party/libvpx/source/libvpx/third_party/googletest/src/src/gtest.cc
index b8f6a5c31cc8..f23a9534f3bc 100644
--- a/third_party/libvpx/source/libvpx/third_party/googletest/src/src/gtest.cc
+++ b/third_party/libvpx/source/libvpx/third_party/googletest/src/src/gtest.cc
@@ -2073,7 +2073,7 @@ AssertionResult CmpHelperSTRNE(const char* s1_expression,
 bool String::CaseInsensitiveCStringEquals(const char * lhs, const char * rhs) {
   if (lhs == nullptr) return rhs == nullptr;
   if (rhs == nullptr) return false;
-  return posix::StrCaseCmp(lhs, rhs) == 0;
+  return strcasecmp(lhs, rhs) == 0;
 }
 
 // Compares two wide C strings, ignoring case.  Returns true if and only if they
diff --git a/third_party/mini_chromium/base/strings/stringprintf.cc b/third_party/mini_chromium/base/strings/stringprintf.cc
index 47b6a2f6f1b1..d4c9a392f3ca 100644
--- a/third_party/mini_chromium/base/strings/stringprintf.cc
+++ b/third_party/mini_chromium/base/strings/stringprintf.cc
@@ -21,7 +21,7 @@ inline int vsnprintfT(char* buffer,
                       size_t buf_size,
                       const char* format,
                       va_list argptr) {
-  return vsnprintf(buffer, buf_size, format, argptr);
+  return base::vsnprintf(buffer, buf_size, format, argptr);
 }
 
 template <class StringType>
diff --git a/third_party/musl/BUILD.gn b/third_party/musl/BUILD.gn
index a03871fba9b9..271590b13b17 100644
--- a/third_party/musl/BUILD.gn
+++ b/third_party/musl/BUILD.gn
@@ -385,7 +385,9 @@ static_library("c_internal") {
     "src/starboard/stdio/stderr.c",
     "src/starboard/stdio/stdout.c",
     "src/starboard/stdio/vfprintf.c",
+    "src/starboard/stdio/vsnprintf.c",
     "src/starboard/stdio/vsscanf.c",
+    "src/starboard/stdio/vswprintf.c",
     "src/starboard/stdlib/strtod_l.c",
     "src/starboard/time/__tz.c",
     "src/starboard/time/clock_gettime.c",
@@ -397,12 +399,11 @@ static_library("c_internal") {
     "src/stdio/snprintf.c",
     "src/stdio/sscanf.c",
     "src/stdio/swprintf.c",
+    "src/stdio/sprintf.c",
     "src/stdio/vasprintf.c",
     "src/stdio/vprintf.c",
     "src/stdio/vsprintf.c",
-    "src/stdio/vsnprintf.c",
-    "src/stdio/vswprintf.c",
-    "src/stdio/vfwprintf.c",
+
     "src/stdlib/abs.c",
     "src/stdlib/atof.c",
     "src/stdlib/atoi.c",
@@ -434,6 +435,7 @@ static_library("c_internal") {
     "src/string/rindex.c",
     "src/string/stpcpy.c",
     "src/string/stpncpy.c",
+    "src/string/strcasecmp.c",
     "src/string/strcat.c",
     "src/string/strchr.c",
     "src/string/strchrnul.c",
@@ -445,6 +447,7 @@ static_library("c_internal") {
     "src/string/strlcat.c",
     "src/string/strlcpy.c",
     "src/string/strlen.c",
+    "src/string/strncasecmp.c",
     "src/string/strncat.c",
     "src/string/strncmp.c",
     "src/string/strncpy.c",
diff --git a/third_party/musl/src/starboard/stdio/vsnprintf.c b/third_party/musl/src/starboard/stdio/vsnprintf.c
new file mode 100644
index 000000000000..b2be99b3763e
--- /dev/null
+++ b/third_party/musl/src/starboard/stdio/vsnprintf.c
@@ -0,0 +1,10 @@
+#include <stdio.h>
+#include "starboard/string.h"
+
+#if SB_API_VERSION < 16
+
+int vsnprintf(char *restrict s, size_t n, const char *restrict fmt, va_list ap) {
+  return SbStringFormat(s, n, fmt, ap);
+}
+
+#endif
diff --git a/third_party/musl/src/starboard/stdio/vswprintf.c b/third_party/musl/src/starboard/stdio/vswprintf.c
new file mode 100644
index 000000000000..a9f932f0b285
--- /dev/null
+++ b/third_party/musl/src/starboard/stdio/vswprintf.c
@@ -0,0 +1,10 @@
+#include <wchar.h>
+#include "starboard/string.h"
+
+#if SB_API_VERSION < 16
+
+int vswprintf(wchar_t *restrict s, size_t n, const wchar_t *restrict fmt, va_list ap) {
+  return SbStringFormatWide(s, n, fmt, ap);
+}
+
+#endif
diff --git a/third_party/v8/src/base/platform/platform-starboard.cc b/third_party/v8/src/base/platform/platform-starboard.cc
index c3bacee28d8e..0a392ee03f7d 100644
--- a/third_party/v8/src/base/platform/platform-starboard.cc
+++ b/third_party/v8/src/base/platform/platform-starboard.cc
@@ -6,8 +6,6 @@
 // abstraction layer for Cobalt, an HTML5 container used mainly by YouTube
 // apps in the living room.
 
-#include <stdio.h>
-
 #include "src/base/lazy-instance.h"
 #include "src/base/macros.h"
 #include "src/base/platform/platform.h"
@@ -23,6 +21,7 @@
 #include "starboard/memory.h"
 #include "starboard/time.h"
 #include "starboard/time_zone.h"
+#include <stdio.h>
 
 namespace v8 {
 namespace base {
diff --git a/url/url_canon_internal.cc b/url/url_canon_internal.cc
index 7294e358f335..a9dd636378d4 100644
--- a/url/url_canon_internal.cc
+++ b/url/url_canon_internal.cc
@@ -9,7 +9,6 @@
 #ifndef EINVAL
 #define EINVAL 22
 #endif
-
 #else
 #include <errno.h>
 #include <stdlib.h>