HTTP Compression Test

This tool checks your server to see if it is sending out compressed data. It will work with any form of compression: mod_gzip, mod_deflate, or gzip compression through any server-side language, like PHP. Only textual data is compressed: HTML, CSS, JavaScript etc. Images are already compressed and are not gzip'ed through a web server. This tool only checks the exact document you enter. To check CSS or JavaScript files, enter the address of that file.

A common misconception is that compressing web pages on the fly will slow down a web server. This is not the case. It does take a little CPU to do the compression, but the result is that your web server is handling significantly less data, which reduces the total CPU load on the server.

Check this out for an easy way to use PHP to gzip compress your pages

Servers with any form of HTTP compression enabled, only send compressed data to browsers that request it. This makes them fully backwards compatible, with the exception of a very few, very old browsers that request compressed content but don't know what to do with it. All modern browsers support compressed content. This box will tell you if the one you are using right now requests gzip: