HTTP Header Mangler is a Firefox add-on which inserts HTTP headers on a per host basis.
Matching of hosts is done with either simple strings or regular expressions.
Rules can have multiple headers apply to multiple hosts, or simply insert a single header for a single host.
# This is a comment.
# Delete headers using "" or ''.
# Indentation is allowed.
# Formatting with whitespace is allowed.
X-Forwarded-For = 100.101.102.103
User-Agent = Mozilla/3.0 (X11; I; AIX 2)
# Here's an incomplete rule, which will be ignored.
Thanks to https://github.com/aexaey for the contribution.
For more information, please visit HTTP Header Mangler on Github.