Varnish is a web app accelerator, which has been gaining a lot of popularity in recent years, as 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 an HTTP reverse proxy as well and is used to lower the overall server load and to boost the access speed for the site visitors. Each time a visitor opens a page on a specific site, the web browser request is taken care of by the web server and the requested content is returned as a response. If the Varnish accelerator is activated, it caches the pages that the website visitor browses and in case any of them is opened once more, it’s delivered by Varnish and not by the server directly. The boost in the performance is due to the fact that the accelerator processes the browser requests substantially faster than any web server, which results in much faster browsing speeds for the visitors. If any data is modified in the meantime, the cached web pages will also be updated the next time somebody attempts to open them.