diff --git a/internal/config/config.go b/internal/config/config.go
index 26dde7d..f8c7869 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -9,7 +9,7 @@ import (
 
 type Config struct {
 	Site                 string            `env:"SITE"`
-	AllowedDomains       string            `env:"ALLOWED_DOMAINS"`
+	AllowedDomains       []string          `env:"ALLOWED_DOMAINS" envSeparator:","`
 	UserAgent            string            `env:"USER_AGENT" envDefault:"govukbot"`
 	Headers              map[string]string `env:"HEADERS"`
 	Concurrency          int               `env:"CONCURRENCY" envDefault:"10"`
diff --git a/internal/config/config_test.go b/internal/config/config_test.go
index 3b93191..9cb7e74 100644
--- a/internal/config/config_test.go
+++ b/internal/config/config_test.go
@@ -25,7 +25,7 @@ func TestNewConfig(t *testing.T) {
 			name: "env vars",
 			envVars: map[string]string{
 				"SITE":                 "example.com",
-				"ALLOWED_DOMAINS":      "example.com",
+				"ALLOWED_DOMAINS":      "example.com,foo.bar",
 				"USER_AGENT":           "custom-agent",
 				"HEADERS":              "Test-Header:Test-Value",
 				"CONCURRENCY":          "20",
@@ -33,7 +33,7 @@ func TestNewConfig(t *testing.T) {
 			},
 			expected: &Config{
 				Site:           "example.com",
-				AllowedDomains: "example.com",
+				AllowedDomains: []string{"example.com", "foo.bar"},
 				UserAgent:      "custom-agent",
 				Headers: map[string]string{
 					"Test-Header": "Test-Value",
diff --git a/internal/crawler/crawler.go b/internal/crawler/crawler.go
index a4f82fa..445c3c1 100644
--- a/internal/crawler/crawler.go
+++ b/internal/crawler/crawler.go
@@ -29,7 +29,7 @@ func NewCrawler(cfg *config.Config) (*Crawler, error) {
 func newCollector(cfg *config.Config) (*colly.Collector, error) {
 	c := colly.NewCollector(
 		colly.UserAgent(cfg.UserAgent),
-		colly.AllowedDomains(cfg.AllowedDomains),
+		colly.AllowedDomains(cfg.AllowedDomains...),
 		colly.DisallowedURLFilters(cfg.DisallowedURLFilters...),
 		colly.Async(true),
 	)