What do you use to inject custom CSS into websites?

Ideally something that'd work across both my main browsers, Firefox and Safari.

@pixelambacht It’s not what I use it for, but StopTheMadness supports this (and I’m otherwise quite happy with the app)

https://underpassapp.com/StopTheMadness

StopTheMadness browser extension

StopTheMadness is a web browser extension that stops web sites from making your browser harder to use.

@jasperlai I opted for Stylus, but StopTheMadness looks like a great extension. Thanks for the suggestion!