Varnish (software)

Varnish is an HTTP accelerator designed for content-heavy dynamic web sites as well as heavily consumed APIs. In contrast to other web accelerators, such as Squid, which began life as a client-side cache, or Apache and nginx, which are primarily origin servers, Varnish was designed as an HTTP accelerator. Varnish is focused exclusively on HTTP, unlike other proxy servers that often support FTP, SMTP and other .

Varnish is used by high-profile, high-traffic websites including , online newspaper sites such as The New York Times, The Guardian, The Hindu, Corriere della Sera, social media and content sites such as Facebook, Twitter, Reddit, Vimeo, and Tumblr. In 2012, 5% of the top 10,000 sites in the web used the software.

The project was initiated by the online branch of the Norwegian tabloid newspaper Verdens Gang. The architect and lead developer is Danish independent consultant Poul-Henning Kamp (a well-known FreeBSD core developer), with management, infrastructure and additional development originally provided by the Norwegian Linux consulting company Linpro. The support, management and development of Varnish was later spun off into a separate company, Varnish Software.

Varnish is free and open source software, available under a two-clause BSD license. Commercial support is available from Varnish Software, amongst others.