HOW TO BRING BACK CLASSIC SQUARE TABS IN RECENT FIREFOX

Tired of round shaped chrome-like tabs?

These tweaks attempt to recreate the feel of Quantum with its squared tabs and menus, but in the Proton UI.
As of FF91, the about:config option to disable proton has been deprecated, leaving CSS as the main way to revert the UI.

Want to bring back minimalistic strict lines and make things more serious?

[Firefox-Proton-Square] tweak will help ya.

INSTALLATION PROCESS

• Enable userChrome.css support
• Go to about:config

toolkit.legacyUserProfileCustomizations.stylesheets  true

• Find Profile Directory
• Go to about:support
• Open Profile Directory
• Copy following files:

userChrome.css
userContent.css
userVariables.css

to your profile directory in chrome folder. Here is my example:

C:\Program Files\Iceweasel_x64\Profiles\chrome\

• Restart Firefox