Use these free tools from to measure and optimize your website. is committed to making website performance and security open and easy for websites of all sizes. That's why we've created these free tools, which enable developers to make more informed website performance decisions and test their caching configurations before running Varnish Cache in production.

tools Developer Tools

Synth by

Synth is a free monitoring tool that provides you with ongoing data on your website performance. Use Synth to collect baseline performance measurements and see how your site scales during high-traffic times.


  • Back end load times
  • Front end load times
  • Full page load times
  • SpeedIndex score
  • Data collected multiple times per day
  • Ability to test your own site and competitors' sites
  • Data visualized in easy-to-read graphs
Sign Up

VCL Fiddle

VCL fiddle, created by the Varnish Cache experts at, allows developers to test their Varnish Cache Configuration Language (VCL) to see how it will run in production.


  • Experiment with Varnish Cache in a sandboxed environment
  • Reproduce a website caching scenario for testing and debugging
  • View HTTP response headers from your VCL
  • Includes 9 versions of Varnish Cache up to Varnish Cache 5.0
  • Provides examples for common VCL setups
Try it now

To learn more about tools or to sign up for beta trials of future tools, please get in touch.