Resource Override от Kyle Paulsen

An extension to help you gain full control of any website by redirecting traffic, replacing, editing, or inserting new content.
This is the ultimate tool for taking control of any website.

Newly added: Request and Response header modification with common use case presets (Enable CORS, force allow outside content, allow iframes... etc).

This extension will allow you to redirect URLs on the fly before requests are made. You can also redirect URLs to text documents that you can create with this extension. If you need to inject JavaScript or CSS files, this extension has you covered.

This tool is great for debugging production websites, as you can edit and inject code on the fly. You no longer have to scan through minified code as you can just redirect to an unminified version or paste in the unminified version with the integrated file editor.