--- a/js/xpconnect/src/XPCJSContext.cpp
+++ b/js/xpconnect/src/XPCJSContext.cpp
@@ -753,29 +753,31 @@ static mozilla::Atomic<bool> sExtraWarni
 bool xpc::ExtraWarningsForSystemJS() { return sExtraWarningsForSystemJS; }
 #else
 bool xpc::ExtraWarningsForSystemJS() { return false; }
 #endif
 
 static mozilla::Atomic<bool> sSharedMemoryEnabled(false);
 static mozilla::Atomic<bool> sStreamsEnabled(false);
 static mozilla::Atomic<bool> sFieldsEnabled(false);
+static mozilla::Atomic<bool> sParserDeferAllocationEnabled(false);
 static mozilla::Atomic<bool> sAwaitFixEnabled(false);
 
 void xpc::SetPrefableRealmOptions(JS::RealmOptions& options) {
   options.creationOptions()
       .setSharedMemoryAndAtomicsEnabled(sSharedMemoryEnabled)
       .setCoopAndCoepEnabled(
           StaticPrefs::browser_tabs_remote_useCrossOriginOpenerPolicy() &&
           StaticPrefs::browser_tabs_remote_useCrossOriginEmbedderPolicy())
       .setStreamsEnabled(sStreamsEnabled)
       .setWritableStreamsEnabled(
           StaticPrefs::javascript_options_writable_streams())
       .setFieldsEnabled(sFieldsEnabled)
       .setAwaitFixEnabled(sAwaitFixEnabled);
+  options.behaviors().setDeferredParserAlloc(sParserDeferAllocationEnabled);
 }
 
 static void LoadStartupJSPrefs(XPCJSContext* xpccx) {
   // Prefs that require a restart are handled here. This includes the
   // process-wide JIT options because toggling these at runtime can easily cause
   // races or get us into an inconsistent state.
   //
   // 'Live' prefs are handled by ReloadPrefsCallback below.
@@ -926,16 +928,18 @@ static void ReloadPrefsCallback(const ch
 
   bool werror = Preferences::GetBool(JS_OPTIONS_DOT_STR "werror");
 
   bool extraWarnings = Preferences::GetBool(JS_OPTIONS_DOT_STR "strict");
 
   sSharedMemoryEnabled =
       Preferences::GetBool(JS_OPTIONS_DOT_STR "shared_memory");
   sStreamsEnabled = Preferences::GetBool(JS_OPTIONS_DOT_STR "streams");
+  sParserDeferAllocationEnabled =
+      Preferences::GetBool(JS_OPTIONS_DOT_STR "parser_defer_allocation");
   sFieldsEnabled =
       Preferences::GetBool(JS_OPTIONS_DOT_STR "experimental.fields");
   sAwaitFixEnabled =
       Preferences::GetBool(JS_OPTIONS_DOT_STR "experimental.await_fix");
 
 #ifdef DEBUG
   sExtraWarningsForSystemJS =
       Preferences::GetBool(JS_OPTIONS_DOT_STR "strict.debug");

--- a/modules/libpref/init/StaticPrefList.yaml
+++ b/modules/libpref/init/StaticPrefList.yaml
@@ -4098,16 +4098,22 @@
   type: uint32_t
 #ifdef NIGHTLY_BUILD
   value: 15000
 #else
   value: 300000
 #endif
   mirror: always
 
+# Defer allocation of GC objects as late as possible in a parse
+- name: javascript.options.parser_defer_allocation
+  type: RelaxedAtomicBool
+  value: false
+  mirror: always
+
 - name: javascript.options.experimental.fields
   type: RelaxedAtomicBool
   value: true
   mirror: always
 
 - name: javascript.options.experimental.await_fix
   type: RelaxedAtomicBool
   value: true