We told you about the new Proton UI when it was under development and testing and was available in Firefox testing versions such as Nightly builds. The new redesigned UI is fresh and modern and has been developed to provide similar interface for different devices. If you upgraded or installed newer versions of Mozilla Firefox web browser such as 89 and later, you might have noticed the new white/grey theme and UI which is called “ Proton UI“. This article will help you in restoring old classic theme and User Interface (UI) in Mozilla Firefox 89.0 and later versions. New Working Method to Restore Classic Theme and UI in Firefox 91 and Later Versions UPDATE: A new working method available at following link to disable new Proton UI and restore classic UI in Firefox 91.0 and later versions:
