Varnish is a website accelerator, which has been gaining a lot in popularity in recent years, as it can increase the loading speed of any site, at times even by one hundred percent, based on the content itself. This tool is occasionally called a caching HTTP reverse proxy too and is used to lower the overall load on the server and to enhance the access speed for the site visitors. Each time a visitor opens a page on a specific Internet site, the web browser request is taken care of by the web server and the requested data is sent as a response. If the Varnish accelerator is activated, it caches the pages that the site visitor browses and if any of them is loaded once more, it is delivered by Varnish and not by the server directly. The performance improvement is due to the fact that the accelerator processes the browser requests considerably quicker than any web server, which results in much faster browsing speeds for the site visitors. In case any content is modified meanwhile, the cached pages will also be updated the next time someone attempts to open them.