diff --git a/js/src/builtin/intl/Collator.cpp b/js/src/builtin/intl/Collator.cpp
index ea1e894b8781..e748e78b63da 100644
--- a/js/src/builtin/intl/Collator.cpp
+++ b/js/src/builtin/intl/Collator.cpp
@@ -19,7 +19,6 @@
 #include "builtin/intl/LanguageTag.h"
 #include "builtin/intl/SharedIntlData.h"
 #include "gc/GCContext.h"
-#include "js/CharacterEncoding.h"
 #include "js/PropertySpec.h"
 #include "js/StableStringChars.h"
 #include "js/TypeDecls.h"
diff --git a/js/src/builtin/intl/CommonFunctions.cpp b/js/src/builtin/intl/CommonFunctions.cpp
index 5bd27621dc66..18bcd011ce06 100644
--- a/js/src/builtin/intl/CommonFunctions.cpp
+++ b/js/src/builtin/intl/CommonFunctions.cpp
@@ -9,14 +9,12 @@
 #include "builtin/intl/CommonFunctions.h"
 
 #include "mozilla/Assertions.h"
-#include "mozilla/Casting.h"
-#include "mozilla/intl/ICU4CGlue.h"
+#include "mozilla/intl/ICUError.h"
 #include "mozilla/TextUtils.h"
 
 #include <algorithm>
 
 #include "gc/GCEnum.h"
-#include "gc/Zone.h"
 #include "gc/ZoneAllocator.h"
 #include "js/friend/ErrorMessages.h"  // js::GetErrorMessage, JSMSG_INTERNAL_INTL_ERROR
 #include "js/Value.h"
@@ -24,8 +22,9 @@
 #include "vm/JSObject.h"
 #include "vm/SelfHosting.h"
 #include "vm/Stack.h"
+#include "vm/StringType.h"
 
-#include "vm/JSObject-inl.h"
+#include "gc/GCContext-inl.h"
 
 bool js::intl::InitializeObject(JSContext* cx, JS::Handle<JSObject*> obj,
                                 JS::Handle<PropertyName*> initializer,
diff --git a/js/src/builtin/intl/CommonFunctions.h b/js/src/builtin/intl/CommonFunctions.h
index f3882cad9c24..ac75d6168810 100644
--- a/js/src/builtin/intl/CommonFunctions.h
+++ b/js/src/builtin/intl/CommonFunctions.h
@@ -7,16 +7,12 @@
 #ifndef builtin_intl_CommonFunctions_h
 #define builtin_intl_CommonFunctions_h
 
-#include "mozilla/Assertions.h"
-
 #include <stddef.h>
 #include <stdint.h>
 #include <string.h>
-#include <type_traits>
 
 #include "js/RootingAPI.h"
-#include "js/Vector.h"
-#include "vm/StringType.h"
+#include "js/Utility.h"
 
 namespace mozilla::intl {
 enum class ICUError : uint8_t;
@@ -24,6 +20,8 @@ enum class ICUError : uint8_t;
 
 namespace js {
 
+class PropertyName;
+
 namespace intl {
 
 /**
@@ -93,7 +91,7 @@ struct OldStyleLanguageTagMapping {
 
 extern const OldStyleLanguageTagMapping oldStyleLanguageTagMappings[5];
 
-extern UniqueChars EncodeLocale(JSContext* cx, JSString* locale);
+extern JS::UniqueChars EncodeLocale(JSContext* cx, JSString* locale);
 
 // The inline capacity we use for a Vector<char16_t>.  Use this to ensure that
 // our uses of ICU string functions, below and elsewhere, will try to fill the
diff --git a/js/src/builtin/intl/DateTimeFormat.cpp b/js/src/builtin/intl/DateTimeFormat.cpp
index 91c4338edb7c..bb5f259b9afb 100644
--- a/js/src/builtin/intl/DateTimeFormat.cpp
+++ b/js/src/builtin/intl/DateTimeFormat.cpp
@@ -9,12 +9,10 @@
 #include "builtin/intl/DateTimeFormat.h"
 
 #include "mozilla/Assertions.h"
-#include "mozilla/EnumSet.h"
 #include "mozilla/intl/Calendar.h"
 #include "mozilla/intl/DateIntervalFormat.h"
 #include "mozilla/intl/DateTimeFormat.h"
 #include "mozilla/intl/DateTimePart.h"
-#include "mozilla/intl/DateTimePatternGenerator.h"
 #include "mozilla/intl/Locale.h"
 #include "mozilla/intl/TimeZone.h"
 #include "mozilla/Range.h"
@@ -25,9 +23,7 @@
 #include "builtin/intl/FormatBuffer.h"
 #include "builtin/intl/LanguageTag.h"
 #include "builtin/intl/SharedIntlData.h"
-#include "builtin/intl/TimeZoneDataGenerated.h"
 #include "gc/GCContext.h"
-#include "js/CharacterEncoding.h"
 #include "js/Date.h"
 #include "js/experimental/Intl.h"     // JS::AddMozDateTimeFormatConstructor
 #include "js/friend/ErrorMessages.h"  // js::GetErrorMessage, JSMSG_*
diff --git a/js/src/builtin/intl/DateTimeFormat.h b/js/src/builtin/intl/DateTimeFormat.h
index ceb95a61bca5..cd93af56c6e7 100644
--- a/js/src/builtin/intl/DateTimeFormat.h
+++ b/js/src/builtin/intl/DateTimeFormat.h
@@ -7,10 +7,8 @@
 #ifndef builtin_intl_DateTimeFormat_h
 #define builtin_intl_DateTimeFormat_h
 
-#include "builtin/intl/CommonFunctions.h"
 #include "builtin/SelfHostingDefines.h"
 #include "js/Class.h"
-#include "js/RootingAPI.h"
 #include "vm/NativeObject.h"
 
 namespace mozilla::intl {
diff --git a/js/src/builtin/intl/DisplayNames.cpp b/js/src/builtin/intl/DisplayNames.cpp
index d082d5a72073..2ddffe03650a 100644
--- a/js/src/builtin/intl/DisplayNames.cpp
+++ b/js/src/builtin/intl/DisplayNames.cpp
@@ -12,42 +12,33 @@
 #include "mozilla/intl/DisplayNames.h"
 #include "mozilla/PodOperations.h"
 #include "mozilla/Span.h"
-#include "mozilla/TextUtils.h"
 
 #include <algorithm>
-#include <cstring>
-#include <iterator>
 
 #include "jsnum.h"
 #include "jspubtd.h"
 
 #include "builtin/intl/CommonFunctions.h"
 #include "builtin/intl/FormatBuffer.h"
-#include "builtin/intl/StringAsciiChars.h"
-#include "builtin/String.h"
 #include "gc/AllocKind.h"
 #include "gc/GCContext.h"
 #include "js/CallArgs.h"
 #include "js/Class.h"
 #include "js/experimental/Intl.h"     // JS::AddMozDisplayNamesConstructor
 #include "js/friend/ErrorMessages.h"  // js::GetErrorMessage, JSMSG_*
-#include "js/GCVector.h"
-#include "js/PropertyAndElement.h"  // JS_DefineFunctions, JS_DefineProperties
+#include "js/PropertyAndElement.h"    // JS_DefineFunctions, JS_DefineProperties
 #include "js/PropertyDescriptor.h"
 #include "js/PropertySpec.h"
-#include "js/Result.h"
 #include "js/RootingAPI.h"
 #include "js/TypeDecls.h"
 #include "js/Utility.h"
 #include "vm/GlobalObject.h"
-#include "vm/JSAtom.h"
 #include "vm/JSContext.h"
 #include "vm/JSObject.h"
 #include "vm/Printer.h"
 #include "vm/Runtime.h"
 #include "vm/SelfHosting.h"
 #include "vm/Stack.h"
-#include "vm/StaticStrings.h"
 #include "vm/StringType.h"
 #include "vm/WellKnownAtom.h"  // js_*_str
 
diff --git a/js/src/builtin/intl/DisplayNames.h b/js/src/builtin/intl/DisplayNames.h
index b4f247b02903..9fd6c63a6284 100644
--- a/js/src/builtin/intl/DisplayNames.h
+++ b/js/src/builtin/intl/DisplayNames.h
@@ -17,8 +17,6 @@
 #include "js/Class.h"  // JSClass, JSClassOps, js::ClassSpec
 #include "js/TypeDecls.h"
 #include "js/Value.h"
-#include "vm/JSObject.h"
-#include "vm/List.h"
 #include "vm/NativeObject.h"
 
 struct JS_PUBLIC_API JSContext;
diff --git a/js/src/builtin/intl/IntlObject.cpp b/js/src/builtin/intl/IntlObject.cpp
index ddf71dfb8225..19e4f5042081 100644
--- a/js/src/builtin/intl/IntlObject.cpp
+++ b/js/src/builtin/intl/IntlObject.cpp
@@ -12,6 +12,7 @@
 #include "mozilla/intl/Calendar.h"
 #include "mozilla/intl/Collator.h"
 #include "mozilla/intl/Currency.h"
+#include "mozilla/intl/Locale.h"
 #include "mozilla/intl/MeasureUnitGenerated.h"
 #include "mozilla/intl/TimeZone.h"
 
@@ -22,19 +23,12 @@
 #include <string_view>
 
 #include "builtin/Array.h"
-#include "builtin/intl/Collator.h"
 #include "builtin/intl/CommonFunctions.h"
-#include "builtin/intl/DateTimeFormat.h"
 #include "builtin/intl/FormatBuffer.h"
-#include "builtin/intl/LanguageTag.h"
-#include "builtin/intl/NumberFormat.h"
 #include "builtin/intl/NumberingSystemsGenerated.h"
-#include "builtin/intl/PluralRules.h"
-#include "builtin/intl/RelativeTimeFormat.h"
 #include "builtin/intl/SharedIntlData.h"
 #include "builtin/intl/StringAsciiChars.h"
 #include "ds/Sort.h"
-#include "js/CharacterEncoding.h"
 #include "js/Class.h"
 #include "js/friend/ErrorMessages.h"  // js::GetErrorMessage, JSMSG_*
 #include "js/GCAPI.h"
@@ -45,7 +39,6 @@
 #include "vm/GlobalObject.h"
 #include "vm/JSAtom.h"
 #include "vm/JSContext.h"
-#include "vm/JSObject.h"
 #include "vm/PlainObject.h"  // js::PlainObject
 #include "vm/StringType.h"
 #include "vm/WellKnownAtom.h"  // js_*_str
diff --git a/js/src/builtin/intl/IntlObject.h b/js/src/builtin/intl/IntlObject.h
index 545af6cc0484..5b79f74e922b 100644
--- a/js/src/builtin/intl/IntlObject.h
+++ b/js/src/builtin/intl/IntlObject.h
@@ -7,7 +7,6 @@
 #ifndef builtin_intl_IntlObject_h
 #define builtin_intl_IntlObject_h
 
-#include "js/RootingAPI.h"
 #include "js/TypeDecls.h"
 
 namespace js {
diff --git a/js/src/builtin/intl/LanguageTag.cpp b/js/src/builtin/intl/LanguageTag.cpp
index 56a4f67c2d60..3372f5d99a41 100644
--- a/js/src/builtin/intl/LanguageTag.cpp
+++ b/js/src/builtin/intl/LanguageTag.cpp
@@ -11,8 +11,6 @@
 
 #include "builtin/intl/StringAsciiChars.h"
 #include "gc/Tracer.h"
-#include "js/CharacterEncoding.h"
-#include "js/TracingAPI.h"
 #include "vm/JSContext.h"
 
 namespace js {
diff --git a/js/src/builtin/intl/LanguageTag.h b/js/src/builtin/intl/LanguageTag.h
index e7a91168a31c..e896411e1959 100644
--- a/js/src/builtin/intl/LanguageTag.h
+++ b/js/src/builtin/intl/LanguageTag.h
@@ -12,12 +12,8 @@
 #include "mozilla/intl/Locale.h"
 #include "mozilla/Span.h"
 
-#include "js/AllocPolicy.h"
-#include "js/GCAPI.h"
 #include "js/Result.h"
 #include "js/RootingAPI.h"
-#include "js/Utility.h"
-#include "js/Vector.h"
 
 struct JS_PUBLIC_API JSContext;
 class JSLinearString;
diff --git a/js/src/builtin/intl/ListFormat.cpp b/js/src/builtin/intl/ListFormat.cpp
index 918887180515..7d11d5acd6af 100644
--- a/js/src/builtin/intl/ListFormat.cpp
+++ b/js/src/builtin/intl/ListFormat.cpp
@@ -8,7 +8,6 @@
 
 #include "mozilla/Assertions.h"
 #include "mozilla/intl/ListFormat.h"
-#include "mozilla/PodOperations.h"
 
 #include <stddef.h>
 
@@ -20,9 +19,6 @@
 #include "js/Vector.h"
 #include "vm/JSContext.h"
 #include "vm/PlainObject.h"  // js::PlainObject
-#include "vm/Runtime.h"      // js::ReportAllocationOverflow
-#include "vm/SelfHosting.h"
-#include "vm/Stack.h"
 #include "vm/StringType.h"
 #include "vm/WellKnownAtom.h"  // js_*_str
 
diff --git a/js/src/builtin/intl/ListFormat.h b/js/src/builtin/intl/ListFormat.h
index 5547d05b4872..da0daa711b67 100644
--- a/js/src/builtin/intl/ListFormat.h
+++ b/js/src/builtin/intl/ListFormat.h
@@ -11,7 +11,6 @@
 
 #include "builtin/SelfHostingDefines.h"
 #include "js/Class.h"
-#include "js/RootingAPI.h"
 #include "js/TypeDecls.h"
 #include "vm/NativeObject.h"
 
diff --git a/js/src/builtin/intl/Locale.cpp b/js/src/builtin/intl/Locale.cpp
index 09ed80bd600c..d508bd0a3463 100644
--- a/js/src/builtin/intl/Locale.cpp
+++ b/js/src/builtin/intl/Locale.cpp
@@ -10,14 +10,12 @@
 
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/Assertions.h"
-#include "mozilla/Casting.h"
 #include "mozilla/intl/Locale.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/Span.h"
 #include "mozilla/TextUtils.h"
 
 #include <algorithm>
-#include <iterator>
 #include <string>
 #include <string.h>
 #include <utility>
@@ -32,7 +30,6 @@
 #include "js/friend/ErrorMessages.h"  // js::GetErrorMessage, JSMSG_*
 #include "js/TypeDecls.h"
 #include "js/Wrapper.h"
-#include "util/StringBuffer.h"
 #include "vm/GlobalObject.h"
 #include "vm/JSContext.h"
 #include "vm/PlainObject.h"  // js::PlainObject
diff --git a/js/src/builtin/intl/Locale.h b/js/src/builtin/intl/Locale.h
index d90b2f9282fc..93b618528a54 100644
--- a/js/src/builtin/intl/Locale.h
+++ b/js/src/builtin/intl/Locale.h
@@ -9,7 +9,6 @@
 
 #include <stdint.h>
 
-#include "builtin/SelfHostingDefines.h"
 #include "js/Class.h"
 #include "vm/NativeObject.h"
 
diff --git a/js/src/builtin/intl/NumberFormat.cpp b/js/src/builtin/intl/NumberFormat.cpp
index eed699302207..21b0db030e3f 100644
--- a/js/src/builtin/intl/NumberFormat.cpp
+++ b/js/src/builtin/intl/NumberFormat.cpp
@@ -22,8 +22,6 @@
 #include "mozilla/UniquePtr.h"
 
 #include <algorithm>
-#include <cstring>
-#include <iterator>
 #include <stddef.h>
 #include <stdint.h>
 #include <string>
@@ -36,20 +34,16 @@
 #include "builtin/intl/FormatBuffer.h"
 #include "builtin/intl/LanguageTag.h"
 #include "builtin/intl/RelativeTimeFormat.h"
-#include "ds/Sort.h"
 #include "gc/GCContext.h"
 #include "js/CharacterEncoding.h"
 #include "js/PropertySpec.h"
 #include "js/RootingAPI.h"
 #include "js/TypeDecls.h"
-#include "js/Vector.h"
 #include "util/Text.h"
 #include "vm/BigIntType.h"
 #include "vm/GlobalObject.h"
 #include "vm/JSContext.h"
 #include "vm/PlainObject.h"  // js::PlainObject
-#include "vm/SelfHosting.h"
-#include "vm/Stack.h"
 #include "vm/StringType.h"
 #include "vm/WellKnownAtom.h"  // js_*_str
 
diff --git a/js/src/builtin/intl/NumberFormat.h b/js/src/builtin/intl/NumberFormat.h
index 0055a975b2ca..a0feb4cb4b3a 100644
--- a/js/src/builtin/intl/NumberFormat.h
+++ b/js/src/builtin/intl/NumberFormat.h
@@ -7,8 +7,6 @@
 #ifndef builtin_intl_NumberFormat_h
 #define builtin_intl_NumberFormat_h
 
-#include "mozilla/Attributes.h"
-
 #include <stdint.h>
 
 #include "builtin/SelfHostingDefines.h"
diff --git a/js/src/builtin/intl/PluralRules.cpp b/js/src/builtin/intl/PluralRules.cpp
index 54f38181952a..b7f9d3c6ca06 100644
--- a/js/src/builtin/intl/PluralRules.cpp
+++ b/js/src/builtin/intl/PluralRules.cpp
@@ -10,13 +10,11 @@
 
 #include "mozilla/Assertions.h"
 #include "mozilla/Casting.h"
-#include "mozilla/intl/NumberFormat.h"
 #include "mozilla/intl/PluralRules.h"
 
 #include "builtin/Array.h"
 #include "builtin/intl/CommonFunctions.h"
 #include "gc/GCContext.h"
-#include "js/CharacterEncoding.h"
 #include "js/PropertySpec.h"
 #include "vm/GlobalObject.h"
 #include "vm/JSContext.h"
diff --git a/js/src/builtin/intl/PluralRules.h b/js/src/builtin/intl/PluralRules.h
index 277e0debbfb5..86d8ec105df6 100644
--- a/js/src/builtin/intl/PluralRules.h
+++ b/js/src/builtin/intl/PluralRules.h
@@ -9,7 +9,6 @@
 
 #include "builtin/SelfHostingDefines.h"
 #include "js/Class.h"
-#include "js/RootingAPI.h"
 #include "vm/NativeObject.h"
 
 namespace mozilla::intl {
diff --git a/js/src/builtin/intl/RelativeTimeFormat.cpp b/js/src/builtin/intl/RelativeTimeFormat.cpp
index 457aec9857ec..c847fe0e6cb2 100644
--- a/js/src/builtin/intl/RelativeTimeFormat.cpp
+++ b/js/src/builtin/intl/RelativeTimeFormat.cpp
@@ -16,7 +16,6 @@
 #include "builtin/intl/FormatBuffer.h"
 #include "builtin/intl/LanguageTag.h"
 #include "gc/GCContext.h"
-#include "js/CharacterEncoding.h"
 #include "js/friend/ErrorMessages.h"  // js::GetErrorMessage, JSMSG_*
 #include "js/PropertySpec.h"
 #include "vm/GlobalObject.h"
diff --git a/js/src/builtin/intl/RelativeTimeFormat.h b/js/src/builtin/intl/RelativeTimeFormat.h
index 3f4500f0b70c..f46aaa217bf9 100644
--- a/js/src/builtin/intl/RelativeTimeFormat.h
+++ b/js/src/builtin/intl/RelativeTimeFormat.h
@@ -15,7 +15,6 @@
 #include "gc/Barrier.h"
 #include "js/Class.h"
 #include "vm/NativeObject.h"
-#include "vm/Runtime.h"
 
 namespace mozilla::intl {
 class RelativeTimeFormat;
diff --git a/js/src/builtin/intl/SharedIntlData.cpp b/js/src/builtin/intl/SharedIntlData.cpp
index 60ccc8464f98..c3cbffc70e6a 100644
--- a/js/src/builtin/intl/SharedIntlData.cpp
+++ b/js/src/builtin/intl/SharedIntlData.cpp
@@ -28,9 +28,7 @@
 
 #include "builtin/Array.h"
 #include "builtin/intl/CommonFunctions.h"
-#include "builtin/intl/LanguageTag.h"
 #include "builtin/intl/TimeZoneDataGenerated.h"
-#include "builtin/String.h"
 #include "js/Utility.h"
 #include "js/Vector.h"
 #include "vm/ArrayObject.h"
diff --git a/js/src/builtin/intl/SharedIntlData.h b/js/src/builtin/intl/SharedIntlData.h
index ba0006348264..8cada7c61bd0 100644
--- a/js/src/builtin/intl/SharedIntlData.h
+++ b/js/src/builtin/intl/SharedIntlData.h
@@ -13,7 +13,6 @@
 #include <stddef.h>
 
 #include "js/AllocPolicy.h"
-#include "js/CharacterEncoding.h"
 #include "js/GCAPI.h"
 #include "js/GCHashTable.h"
 #include "js/Result.h"
diff --git a/js/src/builtin/intl/StringAsciiChars.h b/js/src/builtin/intl/StringAsciiChars.h
index 64408c68e79a..3323544d8c92 100644
--- a/js/src/builtin/intl/StringAsciiChars.h
+++ b/js/src/builtin/intl/StringAsciiChars.h
@@ -11,7 +11,6 @@
 #include "mozilla/Attributes.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/Span.h"
-#include "mozilla/TextUtils.h"
 
 #include <stddef.h>