Varnish Software releases Varnish Cache 4.0

A product for excelling in web content delivery

Faster streaming of large objects

Previous versions of Varnish Cache offered only limited support for streaming. Varnish Cache 4.0 includes full streaming support, cutting down of delivery times for larger objects and decreased latency when accessing content through cache hierarchies.

Security enhancements in Varnish Cache 4.0

Varnish Cache 4.0 introduces the option to set read-only parameters. Once up and running, the read-only parameters can not be changed through the command line interfaces. This reduces the likelihood of people successfully executing an escalation of privileges attack. The ability to include inline C code in the configuration file comes optional with Varnish Cache 4.0 with the default being disabled.

More fine-grained Varnish logging for simple debugging

The logging in Varnish Cache 4.0 is completely refactored, including a query language that enables users to query the log. In addition, the log can now be grouped in various ways showing log items that logically belong together. This makes it possible to request a certain page, with the corresponding backend request, response and any ESI sub-requests grouped together, making debugging of web applications much simpler.

Load balancing directors made easy

With Varnish Cache 4.0, writing a director for load balancing has been made even easier than before. The load balancing directors are now loadable modules and new load balancing schemes can be implemented without having to patch Varnish itself.

Paving the way for the future of HTTP content delivery

The way threading is organized in Varnish Cache 4.0 has been completely rewritten and the request path has changed slightly. Now the client facing front-end threads make requests to the backend server-facing threads when something needs to get done towards the backend. Most of the changes are architectural and allow for full Streaming support as well as asynchronous Background (Stale-While-Revalidate) and Conditional (If-Modified-Since) Backend Requests. This change paves the way for future enhancements like parallel ESI and HTTP 2.0 support.

“Varnish Cache 4.0 will be a major boost for the Varnish community as well as our customers. And an added benefit is that all products and software in Varnish Plus, our commercial offering intended for 10% of our user community, works with Varnish Cache 4.0 from day one,” said Lars Larsson, Varnish Software’s CEO.

The release of Varnish Cache 4.0 was announced at the Varnish Software Summit in London earlier today.

Come celebrate with us!

Varnish Cache 4.0 is the first big release coming out of Varnish Software since 2011. The Varnish Cache community will be celebrating the milestone with more than 30 parties worldwide on April 29th. We hope you’ll joins us in celebrating by joining a party close to you.

If you are unable to join us in person you can join the parties in Oslo, Copenhagen and London on Google Hangout on Air. Register here. We hope to see you there!

Online resources

You can download Varnish Cache 4.0 here.

Further details on Varnish Cache 4.0 can be found here.


About Varnish Software

Varnish Software delivers the world’s most widely used HTTP accelerator based on open source. Varnish Cache was originally developed in Norway and has since spread to 1.6 million sites worldwide. It is currently used by some of the world’s most influential websites such as The BBC, The New York Times, Business Insider, Morningstar, Vimeo, The Canadian Broadcasting Corporation, Die Zeit, Schibsted Media Group, The Hindu and many more. Varnish Software’s business model is to provide support, services and enterprise-level products for Varnish Cache via their primary product Varnish Plus.

Varnish Software is headquartered in Oslo, Norway and has offices in London, New York and Zürich. Its majority owner is Neqst, an investment firm focused exclusively on technology and technology-enabled companies. For more information, please visit:



Hildur Smaradottir, VP, Global Marketing, Varnish Software

Request a free trial