Alternatively, you can selectively reverse your advanced customization and configuration changes, as follows: If Firefox suddenly appears broken after an update, you may need to use the Refresh feature to restore Firefox to a default state while keeping important data.

For this reason, Mozilla does not officially support adding custom style rules with a userChrome.css or userContent.css file, or using the about:config configuration editor to modify preference settings. However, Mozilla highly recommends that only the developers consider these customizations, as they could cause unexpected behavior or even break Firefox.įirefox is a work in progress and, to allow for continuous innovation, Mozilla cannot guarantee that future updates won’t impact these customizations. Two other forms of advanced configuration allow even further customization: about:config preference modifications and userChrome.css or userContent.css custom style rules. The toolbar layout can be customized, numerous settings can be configured, and the Mozilla Add-ons directory contains a massive library of extensions and themes to add additional functionality and make Firefox reflect your own needs and personality.

Firefox advanced customization and configuration optionsįirefox supports a wide range of customization options that are well-suited to all skill levels.

Firefox css style editor