Please sign the addon because Firefox has new policy requiring addons be signed. Until then it has been disabled in the standard release. Thank you for this addon.(9/2020). Code Injector has helped me improve my web programming skills 1024%. Everyday I learn how to customize my user experience and I have a hard time without this. Sure there are others, but this was easy to get started with.

better than other css injectors because changes are persistent, has badge icon (number of rules applied) and many ways of adding css...

Excelent extension

Even user interfaces of million dollar company sites can be frustrating or annoying. JavaScript injection via this plugin has saved me some woes.

Dear Saba, I spent 15 minutes just to manage a login to put this review. It never happened in past 20 years, ever... in short, I loved it that much!
BOSS, I LOVE YOU for this. Nothing simpler could be achieved with almost everything one might need or think of.
It is not worth trying, it is a MUST HAVE. It just replaced 'Custom Style Script 2' from my workflow, happily.

just what i need,thx a lot

Amazingly useful extension.
Also a really great UI (it's always a nice bonus).

Easy to use, good UI design & feature set. Perfect.

helpful. I using it to custom js and css of some chat tools that using on work :D