Varnish is a web app accelerator, which has been gaining a lot of popularity in recent years, as it can increase the load speed of any website, sometimes even by 100 percent, depending on the content itself. This tool is occasionally referred to as an HTTP reverse proxy too and is used to lower the overall load on the physical server and to accelerate the browsing speed for the site visitors. Whenever a visitor loads a page on a certain site, the web browser request is handled by the web server and the requested information is served as a reply. If the Varnish accelerator is activated, it caches the web pages that the website visitor browses and if any of them is opened once again, it’s fetched by Varnish and not by the server directly. The performance increase is due to the fact that the accelerator handles the web requests significantly quicker than any web server, which leads to much faster browsing speeds for the users. If any content is updated in the meantime, the cached pages will also be ‘refreshed’ the next time somebody attempts to open them.