We here at Port80 look at lots of tools to monitor HTTP requests and responses.
Some of the tools are implemented as proxies, allow rewriting of headers and all sort of fun stuff, while others plug-in to the browser and monitor the requests passively. While folks may know of LiveHeaders for Mozilla (http://livehttpheaders.mozdev.org) or HttpWatch for IE (http://www.httpwatch.com), here are a few more that we have found varying in price and capabilities.
Stuck in the middle with you -- a few proxies:
Fiddler
http://www.fiddlertool.com/fiddler
We quite like this proxy, which is being updated all the time.
HTTPCatcher
http://www.httpcatcher.com
A Java-based HTTP proxy to see full headers -- and change ‘em on the fly.
Charles
http://www.xk72.com/charles/index.html
Another Java-based HTTP inspection proxy.
Toolbars! Toolbars! Get your HTTP toolbars here!:
IE Inspector - HTTP Analyzer
http://www.ieinspector.com
Similar to the popular HttpWatch but cheaper -- the DOM inspector though is much more interesting...
HTTPLook
http://www.httpsniffer.com/index.htm
Interesting integration with the specification to show you header information and decent filtering.
HttpDetect
http://www.effetech.com/sniffer
This is a packet sniffer that can see all the HTTP stuff going on – on your box. When you need a powertool, Bob Villa-style.
IEWatch
http://www.iewatch.com
Yet another IE plug-in -- is there a pattern of free tools emerging here?
ieHTTPHeaders
http://www.blunck.info/iehttpheaders.html
Yet another IE plug-in -- but this one is FOSS for the budget-minded (free and open, baby).
We even have our own internal tool (httpScope) that we use internally. It may one day be released at a Port80 near you…
Cheers,
Port80ians