COMMAND REFERENCE

fxcss changelog

bash

fxcss changelog --against /path/to/old/firefox --firefox /path/to/new/firefox

What actually changed between two Firefox releases. Compares the chrome IDs and classes collected from both builds and tells you which of the removals your theme depends on:

example

  Firefox 140.13.0 → 153.0.3
    52 chrome names gone, 221 new

  2 of them are used by this theme:
    #urlbar-background          chrome/parts/headerbar-urlbar.css:52
    #urlbar-go-button           chrome/parts/buttons-fixes.css:202

Point it at an ESR build and current release to see what a year of Firefox did to your theme, or at a Beta to find out what is about to break before your users do. --show-all lists every name that changed, not just the ones you use.

--against supplies the older baseline; --firefox supplies the newer target. Use --baseline with a saved snapshot when the old build is no longer installed. Run fxcss audit --firefox beta to investigate findings against a selected channel.

Getting started fxcss audit