Varnish is a web app accelerator, which has been gaining a lot of popularity lately, because it can increase the load speed of any website, sometimes even by one hundred percent, based on the content itself. This tool is sometimes called a caching HTTP reverse proxy as well and is used to decrease the overall load on the physical server and to boost the browsing speed for the site visitors. Every time a visitor accesses a page on a specific website, the web browser request is processed by the web server and the requested data is returned as a reply. If the Varnish accelerator is enabled, it caches the pages that the website visitor browses and in case any of them is opened once again, it is delivered by Varnish and not by the server directly. The boost in the performance is due to the fact that the accelerator handles the web requests substantially quicker than any web server, which results in much faster browsing speeds for the website visitors. If any content is edited in the meantime, the cached web pages will also be updated the next time someone opens them.