Introduction to Varnish

The basics

Varnish Cache is a web application accelerator also known as a caching HTTP reverse proxy. You install it in front of any server that speaks HTTP and configure it to cache the contents. Varnish Cache is really, really fast. It typically speeds up delivery with a factor of 300 - 1000x, depending on your architecture. A high level overview of what Varnish does can be seen in this video.


Varnish performs really, really well. It is usually bound by the speed of the network, effectively turning performance into a non-issue. We’ve seen Varnish delivering 20 Gbps on regular off-the-shelf hardware.


One of the key features of Varnish Cache, in addition to its performance, is the flexibility of its configuration language, VCL. VCL enables you to write policies on how incoming requests should be handled. In such a policy you can decide what content you want to serve, from where you want to get the content and how the request or response should be altered. And, you can extend Varnish with modules (VMODs). You can read more about this in our tutorial.

Further reading

There is a good article describing Varnish Cache on Wikipedia.

License and origin

Varnish is free software licensed under a two-clause BSD licence, also known as the FreeBSD license. The project was initiated in 2005. Varnish Cache 1.0 was released in september 2006.

The name “Varnish”

The name Varnish comes from when the instigator of Varnish spent a long time staring at an art-poster with the word “Vernissage” and ended up checking it in a dictionary, which gives the following three meanings of the word:

r.v. var·nished, var·nish·ing, var·nish·es

  1. To cover with varnish.

  2. To give a smooth and glossy finish to.

  3. To give a deceptively attractive appearance to; gloss over.

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About this website

This site is statically generated. Powered by Sphinx running on Apache httpd on top of FreeBSD. It flies thanks to Varnish Cache. :-)