Header Editor is a free Firefox extension designed for web development, allowing users to modify request and response headers as well as the response body. With its straightforward interface, it facilitates the cancellation and redirection of requests, making it a valuable tool for developers looking to test and debug their web applications. The extension is lightweight and free from advertisements or data collection, ensuring a seamless user experience.

This extension is particularly useful for those engaged in web development, as it provides essential features to manipulate headers effectively. Users can also benefit from a lite version, access the source code, report bugs, and contribute to translations. For those wanting to stay updated with the latest features, a self-distribution version is available for installation.