This online Test GZip Deflate Compression 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, ASP, ASP.NET, Java. 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.