Stylo is ready for community testing on Nightly!

Quantum CSS, aka Stylo, aims to integrate Servo’s parallelized CSS style system written in Rust into Gecko.

Stylo is built with Firefox Nightly and is now ready for wider community testing. If you are using Firefox Nightly, you need to flip the pref layout.css.servo.enabled to true so as to use Stylo.

If you want to help test Stylo but haven’t yet installed Firefox Nightly, install it from and don’t hesitate to have a look at our community documentation about Nightly.

You can ask developers questions about Stylo in the #servo IRC channel (, if you find  a bug please file it in our Bug tracker, Bugzilla. The component to file your bugs  in is Core::CSS Parsing and Computation and start your summary field with Stylo:.

Here is a shortcut url to file bugs in this component:
New Stylo bug – Core::CSS Parsing and Computation

Stylo is making Firefox Nightly rendering of pages even faster and we are now working on chasing correctness and stability bugs so as to ship Stylo by default in Firefox 57, help us build this faster browser today, find and report bugs!

2017-09-06 update:

11 comments on “Stylo is ready for community testing on Nightly!”

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  1. JAn wrote on

    Do I need to restart Nightly after changing the preference value?


    1. Pascal Chevrel wrote on

      No you don’t, just reloading tabs will work.


  2. Shawn Nock wrote on

    layout.css.servo.enabled: option not present in Firefox for Android, 56.0a1 (7-25-17, armeabi-v7a)


    1. Ludovic wrote on

      Pascal forgot to tell this is desktop only for now.


  3. Paul wrote on



  4. dc_coder_84 wrote on

    Unfortunately this flag is not available in Ubuntu so I can’t use it. I am installing via (Ubuntu 16.04). Under about:support I can see it is “disabled by build”.


    1. Pascal Chevrel wrote on

      That’s why we ask our community to not use external repositories for Nightly but Mozilla builds which work fine (Ubuntu user myself).


      1. dc_coder_84 wrote on

        Cool, thanks for the tip 🙂


  5. Pomax wrote on

    This article needs a tiny bit of JS so that it changes the title to “Stylo is ready for community testing by you, right now!” as a little reward for people who are reading this article while already using Nightly =)


  6. morplenauta wrote on

    An example of what Stylo do ?


  7. Julian Viereck wrote on

    Is it worth adding a link to this amazing blog post about what Stylo does and how it works?


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