Modify Headers is a Firefox extension which allowes you to 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 the W3C guide: http://www.w3.org/Protocols/HTTP/HTRQ_Headers.html
· Mozilla Firefox
What's New in This Release: [ read full changelog ]
· Fixed bug 24593: Addon toolbar is always displayed when a new window is opened.