Gzip is a free and open compression method, developed by the GNU project (the same project responsible for a good portion of GNU/Linux). Gzip is also an RFC 1952 standard and is the most popular method for web compression. What essentially happens is that the browser (client) contacts the site (host) and receives a header that indicates that the file can be compressed with gzip. If the browser supports gzip, it will respond and retrieve the compressed file, extract the contents, and display. As a result, it takes less time to download content, thus reducing stress on the server.

Gzip can reduce response size by 70%, which means a tremendous amount of savings on bandwidth. Furthermore, nearly 90% of browsers used on the Internet support it, which includes all modern browsers. The older ones that do not support it are fading away quickly. Apache 1.3 uses a module called mod_gzip, while Apache 2 uses one called mod_deflate. Many content management systems have support for gzip compression built into the backend, if the user choose to enable it.