Just to rule out the obvious first, have you put the user.js file in your profile directory, ie the one that starts with a load of random letters and numbers. Mine is at /home/joe/.mozilla/firefox/h450yc7b.default-release/user.js and works fine.

Yes I did :(. I clicked the root profile on my default profile and i did copy over the files. I also tried it with a non-default profile. Then I opened that profile and nothing happened. I had the same issue in my previous arch installation which I wiped, then installed artix linux openrc, which is now.

Very odd. I've looked at the Arch Wiki and it certainly should work.

The only other remote possibility that springs to my mind would be a permissions error. If I get into my Profile directory and run ls -l user.js I get:—

-rw-r--r-- 1 joe joe 957 Aug 27 17:31 user.js

which is 644 in octal.

You may get better answers on Arch's forum; I'm on Debian so am not familiar with any quirks it may have.

What Firefox version are you using (Mozilla, Snap, Flatpak) as some keep their profile in a different location?

You can use the button in "Help -> More Troubleshooting Information" (about:support) to go to the current Firefox profile folder or use the about:profiles page (Root directory).

• Help -> More Troubleshooting Information -> Profile Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data