Locate and open your profile folder using about:supportĬlick on ☰ ➝ Help ➝ 'More Troubleshooting Information' or navigate to about:support in your address bar. Search for and toggle it to true (by double clicking on it).įor a visual walkthrough Watch Me Do or Youtube. Navigate to about:config in the address bar and accept the risks. Setup Enable userChrome customization in about:config

You can see a complete list of about: pages at about:about. About pages include things like the new tab page (about:newtab), the options page (about:preferences), addons page (about:addons), and so on.

UserContent.css affects the browser's content, that is web content as well as Firefox built-in pages (about: pages) and also extension content.

This includes things like the address bar and tabs, as well as the menus (even the context menu). UserChrome.css affects the browser's chrome (a general term for a UI). You can define these rules in two files, userChrome.css and userContent.css.

This allows virtually unlimited customization of the style of the browser, as well as some very limited functionality customization.

Highlight userChrome.css in browser toolboxįirefox supports advanced customization of its UI with user-defined CSS.

Locate and open your profile folder using about:support.

Enable userChrome customization in about:config.

Firefox css style examples