Varnish is a web app accelerator, which has been gaining a lot in popularity in recent years, as it can increase the speed of any website, at times even by 100 percent, based on the content. This tool is occasionally referred to as a caching HTTP reverse proxy as well and is used to lower the overall load on the physical server and to enhance the access speed for the website visitors. Anytime a visitor loads a page on a specific site, the browser request is taken care of by the web server and the requested content is delivered as a reply. If the Varnish accelerator is activated, it caches the web pages that the visitor opens and in case any of them is opened once again, it is delivered by Varnish and not by the server directly. The increase in the overall performance comes from the fact that the accelerator handles the browser requests significantly quicker than any web server, which results in much faster browsing speeds for the users. If any data is edited meanwhile, the cached pages will also be updated the next time somebody attempts to access them.