Are We Fission Yet?

Fission is the Firefox project to implement process isolation per-site (eTLD+1). In a Fission-world, a webpage serving multiple cross-site iframes will be rendered over multiple processes, while multiple tabs or iframes from the same site will share the same process.

You can learn more about Fission on the the wiki or on mana. The Fission team can be reached at #fission on slack or #domfission on IRC.

If you have questions about or find issues with this site, the source is available here.

Continue reading for a list of projects tracked on the site.

Milestone 4.1

Fission's current milestone 4.1 aims to get all relevant mochitests to successfully pass in a Fission world. They are currently being run as a tier2 job on mozilla-central and can be seen in the M-fis suite. This can be tracked on the burndown chart.

More details of the failing tests can be found in this doc and tips to get started on fixing these tests can be found on the wiki.

Milestone 5

Make Fission functional and stable enough for day to day testing with internal teams.

This can be tracked on the burndown chart.


We are replacing uses of nsIDocShellTreeItem with BrowsingContext.

This can be tracked on the burndown chart and the metabug.


DevTools Fission work is tracked as "M1" (Multiprocess Browser Toolbox) and "M2" (Real Fission Support).

The can be tracked on the burndown chart.