Modify Headers is a Firefox extension that can be used to easily add, modify and filter http request headers. You can modify the user agent string, add headers to spoof a mobile request (e.g. x-up-calling-line-id) and much more. Take a look at the help tab of the Modify Headers window.

Some people think that 'user-agent' is a custom way of specifying the user agent string. This is not true, for a guide on this and other HTTP request headers, look at this W3C page.

Requirements:

· Firefox 1.0 – 3.0*

What's New in This Release: [ read full changelog ]

· Adds support for Firefox 3.0b1.
· Fixes a minor bug with header importing.