I did managed to cast. follow the instructions, Ive added some pictures from: Firefox (95.0.2 64 bit) on Windows 10 (21H1 Build 19043.1415) to: chromecast audio I installed fx_cast add-on from: https://hensm.github.io/fx_cast/ I also installed: fx_cast_bridge-0.1.0-x64.exe a link taken from fx_cast site: https://github.com/hensm/fx_cast/releases/download/v0.1.0/fx_cast_bridge-0.1.0-x64.exe but you should find it also at the site itself after doing so open Firefox's add-on manager (extensions), On the fx_cast settings (press on settings and scroll down) I've added: https://music.youtube.com to the whitelist closed and re-opened Firefox after re-opening Firefox and browsing to https://music.youtube.com the CAST symbol appeared just as in Chrome browser. p.s (not sure it's needed) another thing I did was to add a custom value to Firefox preferences: open a new tab and "browse" to about:config add/change to Value: browser.casting.enabled = true hope it helps.