Varnish is a web accelerator, which has been gaining a lot of popularity in recent years, because it can increase the loading speed of any Internet site, sometimes even by one hundred percent, based on the content. This tool is sometimes referred to as a caching HTTP reverse proxy as well and is used to lower the overall load on the physical server and to increase the access speed for the site visitors. Every time a visitor loads a page on a specific website, the browser request is processed by the web server and the requested data is returned as a response. If Varnish is activated, it caches the web pages that the site visitor opens and in case any of them is opened again, it is delivered by Varnish and not by the server directly. The performance increase is due to the fact that the accelerator handles the browser requests tremendously faster than any web server, which results in much faster browsing speeds for the site visitors. In case any data is modified in the meantime, the cached webpages will also be ‘refreshed’ the next time someone tries to open them.