Custom user.js with privacy, usability, and some personal configs
Copy the user.js file to your Firefox profile folder. Common Firefox profile locations:
Windows:
C:\Users\<username>\AppData\Roaming\Mozilla\Firefox\Profiles\xxxxxxxx.profile-name
macOS:
Users/<username>/Library/Application Support/Firefox/Profiles/xxxxxxxx.profile-name
Linux (native package/AppImage):
/home/<username>/.mozilla/firefox/xxxxxxxx.profile-name
Linux (flatpak):
/home/<username>/.var/app/org.mozilla.firefox/.mozilla/firefox/xxxxxxxx.profile-name
Linux (snap):
/home/<username>/snap/firefox/common/.mozilla/firefox/xxxxxxxx.profile-name