Mozilla released yesterday version 54 of the Firefox browser, which has expanded the multi-process feature from two to five processes (one for the UI, four for browser content).
Mozilla launched multi-process support in August last year, with the release of Firefox 48, but the organization only split Firefox's process into two, one for the browser's UI, and one for handling web page content.
Back in 2016, and again in February 2017, Mozilla engineers promised to improve multi-process support in the coming releases.
Firefox 54 is an intermediary step to the goal of having a Firefox release with unlimited multiple processes, similar to how Chrome works. In Firefox 54, engineers increased the number of content processes to four. The image below shows how this works.
In addition to increasing the number of content processes, Mozilla also rolled out the feature to more users. When multi-process support launched last year, the feature was rolled out only to 1% of the Firefox userbase, only to those running barebones Firefox browsers, with no add-ons. The number of users who received multi-process support — also known as Electrolysis or e10s — has now expanded to Firefox users who use e10s-compatible add-ons. Users who still use older, non-e10s-compatible add-ons will have to wait.
Firefox power-users can adjust the number of content processes today and boost it to 10, 20, or whatever number they like. Just open a new tab and access the "about:config" page. Here, search for "dom.ipc.processCount" and adjust the default value to the one you'd like.
These new features have made an impact in Firefox's performance and allowed v54 to perform better in Mozilla's internal benchmark tests in terms of RAM usage.
Besides the improved multi-process support Mozilla rolled out yesterday, Firefox 54 also expanded the WebExtensions API, its new cross-browser add-ons API, modeled after the one used by Chrome, Vivaldi, Opera, Edge, and others.
The revamped API premiered last year in Firefox 48, and engineers said it will slowly roll out and replace the old Add-ons API by Firefox 57, set for release in November 57, when only add-ons built on the new WebExtensions API will work in Firefox.