Welcome to the wonderful world of Web Performance is a set of Open Source tools that helps make your web pages faster. The coach gives you performance advice based on best practices for your site. Browsertime collects metrics and HAR files from your browser. PageXray converts a HAR file to a usable JSON structure that tells you more about your page. And finally is the main tool that uses all the previously mentioned tools and add supports for testing multiple pages as well as adds the ability to report the metrics to a TSDB (currently Graphite and soon also InfluxDB).

Try out by installing using npm/yarn/Docker (need help?):


$ docker run --privileged --shm-size=512m --rm -v "$(pwd)":/ sitespeedio/


$ npm install -g
$ -h

4.7.0 - Compress the HAR files

With the new release we bug fixed the Slack plugin and made it possible to compress HAR files. Read the blog post to find out more or read the Changelog for all the latest changes.

Be a performance hero!

Pippi Longstocking a true hero

With it’s easy to become a performance hero! Check out our example dashboard, it’s a great example that shows you what you can do. With 4.0 it’s super easy to get that up and running. You can even use our new Docker Compose file to get Graphite/Grafana with default dashboards up and running in less than 5 minutes!

There’s a new Coach in town

I'm the coach

The Godfather of web performance tools YSlow is dead. It died a couple of years after the first release and finally there’s something new that can guide you in the web performance jungle: The Coach gives you advice on how you can make your web page more performant.

Docker to the rescue!

Use our Docker containers to get an environment with Firefox, Chrome, XVFB and up and running as fast as you can download them.

$ docker pull sitespeedio/
$ docker run --rm -v "$(pwd)":/ sitespeedio/ -b firefox

Upgrade to 4.0!

  • HTTP/2 support
  • You can write your own plugins
  • The coach is the new YSlow
  • Generic dashboard templates
  • HAR files as seen by the browser
  • Completely rewritten code base to make it easier to update in the future

Browsertime 1.0 (soon)


We’ve been working on releasing 1.0 of Browsertime for some time now and we will soon be there. We have two things we want to correct first. We want to change the error handling, so errors that occur are reflected in the resulting JSON. It would also be cool to be able to add request headers. Let us know if you can help us!

Thank you! is built upon Open Source tools, we have a special place in our hearts for those projects (see the full list):


You can make better! Check the help section and the full issue list. There’s a lot that needs to be done!

These people has already improved with pull requests or ideas (massive love!).