(Chrome, Firefox, Edge): Violentmonkey is a userscript manager that's similar to Tampermonkey. It's available for Chrome, Firefox, and Edge.
Which userscript manager should I choose these days? : r/firefox tampermonkey alternative
Handles multiple storage requests well and is exceptionally lightweight. tampermonkey alternative
So I went looking for alternatives. Not because Tampermonkey is bad—it's brilliant. But because no brilliant tool should become the only tool you trust. tampermonkey alternative
"I invented this game. I don't need to run fast."
Excellent integration with Firefox's strict security model.