Perform the same request against two HTTP servers and diff the results. For best results use in a terminal that supports ANSI escape sequences.
go get github.com/jgrahamc/httpdiff go install github.com/jgrahamc/httpdiff
Simple usage is to give it two URLs to fetch and it will diff the results. If the bodies are different they are saved to temporary files.
httpdiff http://www.google.co.uk http://www.google.com/
It's also possible to set the Host header to something other than what's in the URIs. This is sometimes useful when testing a temporary set up or when moving servers.
httpdiff -host example.com http://example.old.com/ http://example.new.com
Specific headers can be ignored with the -ignore option
httpdiff -ignore Set-Cookie,Date http://x.com http://y.com
The default HTTP method is GET but that can be changed
httpdiff -method HEAD http://example.com http://example2.com