--- a/browser/app/profile/firefox.js
+++ b/browser/app/profile/firefox.js
@@ -1640,8 +1640,11 @@ pref("toolkit.pageThumbs.minHeight", 190
 #ifdef NIGHTLY_BUILD
 // Enable speech synthesis, only Nightly for now
 pref("media.webspeech.synth.enabled", true);
 #endif
 
 pref("browser.esedbreader.loglevel", "Error");
 
 pref("browser.laterrun.enabled", false);
+
+// Enable browser frames for use on desktop.  Only exposed to chrome callers.
+pref("dom.mozBrowserFramesEnabled", true);

--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -5195,8 +5195,10 @@ pref("toolkit.pageThumbs.minHeight", 0);
 pref("webextensions.tests", false);
 
 // Allow customization of the fallback directory for file uploads
 pref("dom.input.fallbackUploadDir", "");
 
 // Turn rewriting of youtube embeds on/off
 pref("plugins.rewrite_youtube_embeds", true);
 
+// Disable browser frames by default
+pref("dom.mozBrowserFramesEnabled", false);