Flash of unstyled content (FOUC) in Firefox only? Is FF slow renderer?

April 20, 2023 by Tarik

If you add a dummy <script> tag right after <body>, Firefox will show the page after all the css from <head> is loaded:

<body>
   <script>0</script>
   <!-- rest of the code -->
</body>

There is an official bugreport about this FOUC (Flash Of Unstyled Content) on the Firefox site: https://bugzilla.mozilla.org/show_bug.cgi?id=1404468