figby.com

A post of Simon’s reminded me about Live HTTP Headers, a Firefox extension I have used before, but had neglected to install on the new version of Firefox. This tool lets you watch the headers sent between web servers and your browser, and look at them for any page you’ve loaded.

This might sound purely like a toy for web server developers, but it’s actually very useful for anyone who runs a web site. I’ve found it handy for a few recurring situations in particular: first, to find out whether web server features like gzip compression or caching are working properly.

Second, if you run a complex web site, especially one with advertisements, you’ve probably run into this situation before: pages are loading slowly, or not at all, or only displaying partially. Is the problem your overloaded web server? A delay on the server that hosts an image? A delay or downtime with an ad network? That 3rd-party web counter you installed the other day? One look at the HTTP headers after loading a page will tell you what you need to know.

Third, like Simon did with Google Maps, you can use it for an inside look at the operation of someone else’s web site.

Oh, one more thing: if your site uses cookies, you can view all of the cookies and their values in the headers, which has saved me lots of time debugging my sites.