diff --git a/_extensions/embedio/pdf.lua b/_extensions/embedio/pdf.lua
index e5932e3..cc4a7b3 100644
--- a/_extensions/embedio/pdf.lua
+++ b/_extensions/embedio/pdf.lua
@@ -1,5 +1,9 @@
 local function pdf(args, kwargs, meta)
 
+  if not quarto.doc.is_format("html") then
+    return
+  end
+
   -- Supported options for now
   local pdf_file_name = pandoc.utils.stringify(kwargs["file"])
   local height = pandoc.utils.stringify(kwargs["height"]) or "600px"
diff --git a/_extensions/embedio/revealjs.lua b/_extensions/embedio/revealjs.lua
index 42ed162..094bbea 100644
--- a/_extensions/embedio/revealjs.lua
+++ b/_extensions/embedio/revealjs.lua
@@ -25,6 +25,11 @@ local function ensureSlideCSSPresent()
 end
 
 local function revealjs(args, kwargs, meta , raw_args)
+  
+  if not quarto.doc.is_format("html") then
+    return
+  end
+
   -- Enable CSS
   ensureSlideCSSPresent()