Modify requests, inject JavaScript and CSS into pages.
Very powerful extension. It's Tampermonkey power 10. In addition to inject JavaScript and CSS into pages, you can block or redirect requests, modify request and response headers, modify network responses. Thank you Hoang for this.
https://codelab.rs/
https://tamper.dev
beDev
ShuangYa
https://pentestkit.co.uk/
https://petasittek.com
Vinay Kaparthi
cristi.lupascu
http://jacksbrain.com/
https://anthonycossins.com/
Bohumil Beran
https://modheader.com