Varnish is a web application accelerator, which has been gaining a lot in popularity in recent years, because it can increase the load speed of any website, sometimes even by 100 percent, based on the content. This tool is sometimes referred to as an HTTP reverse proxy as well and is used to decrease the overall load on the server and to improve the browsing speed for the site visitors. Anytime a visitor opens a page on a given site, the browser request is handled by the web server and the requested information is returned as a response. If the Varnish accelerator is enabled, it caches the web pages that the visitor opens and if any of them is opened once again, it’s delivered by Varnish and not by the server directly. The increase in the performance comes from the fact that the accelerator handles the web requests substantially faster than any web server, which leads to much faster browsing speeds for the users. In case any data is edited in the meantime, the cached pages will also be updated the next time somebody tries to open them.