At first it's created for redirecting Google Ajax/Api/Themes to other CDN to bypass Great Firewall since pages referring those are slow as molasses.
For now, more features have been added to it, mainly:
- Block url
- Modify Headers
- Test user-defined rules
- Export/Import rules, sync between Firefox and Chrome
- A new UI built with ClojureScript + Reagent ❤️
Most users prefer gooreplacer than other similar extensions(HTTPS Everywhere/Redirector) for ease-of-use. Why not give it a try?
You can find more guides in Github README.