CSS compression enables to reduce drastically the size of the exchanged data between the server and the browser.
Steps can be enabled in the Backend as follows:
In the module “Install” > “All configuration”, set compression level between 1 and 9, where 1 is least compression and 9 is greatest compression. Suggested and most optimal value is 5.
$GLOBALS['TYPO3_CONF_VARS']['BE']['compressionLevel'] = 5;
In a .htaccessfile or in virtual host add some configuration provided by file misc/advanced_htaccess.
Followingthose 2 steps will generate a compressed file and therefore add a “gzip” suffix to the file.
Itmay happen that the browser does not support GZIP compression for some reason. Typically, it can be behind a proxy server which does not support GZIP headers. In this case, the compressor will detect it and send the un-compressed files.