Varnish is a web application accelerator, which has been gaining a lot in popularity in recent years, because it can increase the speed of any site, sometimes even by one hundred percent, based on the content. This tool is occasionally called an HTTP reverse proxy too and is used to decrease the overall load on the server and to enhance the access speed for the site visitors. Every time a visitor loads a page on a particular site, the web browser request is handled by the web server and the requested information is sent as a reply. If Varnish is enabled, it caches the web pages that the website visitor browses and if any of them is accessed once again, it is fetched by Varnish and not by the server directly. The improvement in the overall performance comes from the fact that the accelerator processes the browser requests significantly faster than any web server, which results in much faster browsing speeds for the users. In case any data is changed in the meantime, the cached pages will also be updated the next time somebody attempts to access them.