I have made a JS code and so far it works like a sharp knife, so many thanks for you. I'd suggest for improvements :
1- enable paste option in the code area, you have included copy and cut but I can't past in it.
2- make the same function for android app, I searched a lot but can't find the same thing
3- make the file section more effective, instead of making the user write the pathway of the file, you add an option to select and upload

I have been using this extension for months now. Everything works just fine except when "On page load" feature deselected. Sometimes it is not injecting the code when that feature deselected.

Has been my favorite for a long time but the project seems dead. It has some issues, like loading from file or URL doesn't work and on new tabs, opened in the background, scripts are not applied.

Can't inject on page load on some sites. Have to click "inject" manually and then everything works.

Does its job perfectly. Only thing I'd ask for is other injection options than the click on addon -> click arrow of code -> inject or just on page load. Interval would be nice, also a quicker manual way would be good.

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

buggy, no selection of width and height

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.