Mod_deflate is a module for the Apache Web Server. Its purpose is to make a better use of the available bandwidth by compressing content delivered from the web server to the client's browser. The compression is automatic, and the only requirement is that the browser supports gzip compression. Nowadays, most of the browsers support gzip, and no additional software is required.
The browser will announce if the compression method is supported when sending a request to the server for a specific file, for instance, http://www.example_domain.com/index.html. In case Apache is configured with mod_deflate, the content of index.html will be compressed and sent to the browser. The browser, on the other hand will decompress the gzip file and will display it to the client as a simple html file. The web visitor would not be aware of the above operations.
To set up mod_deflate, you have to create a .htaccess file (note the dot(".") at the beginning of the file) with the following code in it: