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Hostdog is excited to add one more toll in it's toolbox, you may get it enabled by default in our SSD shared hosting packages or ask us to help you install it on your VPS or Dedicated server.

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 the video attached to this web page.


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).

Licence and origin

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

Other features

Varnish Cache also features:

  • Plugin support with Varnish Modules, also called VMODs
  • Support for Edge Side Includes including stitching together compressed ESI fragments
  • Gzip Compression and Decompression
  • DNS, Random, Hashing and Client IP based Directors
  • Technology preview for HTTP Streaming Pass & Fetch
  • Experimental support for Persistent Storage, without LRU eviction
  • Saint and Grace mode