Mozilla supplies multi-process Firefox to <1% of users

Firefox 48 ships with first phase of 'e10s;' some won't see changes until early 2017

mozilla firefox primary
Credit: Rob Schultz

Mozilla on Tuesday began a limited release of a multiple-process Firefox by outfitting fewer than one in every 100 users with the improved browser.

The reworked Firefox 48 was the culmination -- or at least the beginning of that -- of a seven-year effort to boost the browser's performance and improve its stability.

"Users should experience a Firefox that is less susceptible to freezing and is generally more responsive to input," said Nick Nguyen, who leads the Firefox team, in a post to a company blog.

"Electrolysis" -- "e10s" in shorthand -- has been Mozilla's long-term project to separate Firefox's operation into more than one CPU process. The practice lets the browser take advantage of multi-processor systems for heightened performance, and segregates the browser's user interface (UI) and content to keep Firefox from fully crashing when a website or web app fails.

Other browsers, including Apple's Safari and Google's Chrome, already support multiple processes, albeit differently. Safari relies on a single process for the rendering engine, then spawns a new process for each tab's content. Meanwhile, Chrome assigns a new rendering process to each new tab. As a general rule, the Chrome approach uses more device memory than the Safari model.

Mozilla has talked about a multi-process Firefox since 2009. After taking a pause of several years, engineers resumed work in mid-2015.

As a manager outlined eight weeks ago, Mozilla is taking a cautious approach to rolling out the changed Firefox. At this point, only about 1% of roughly half of the user base has been given the multi-process version of Firefox 48. That half, Mozilla has determined, were the best candidates because they didn't rely on add-ons, the biggest stumbling block to e10s.

Because the aged extension model assumed that the browser and content used the same memory space, existing add-ons must be modified. Mozilla's list of e10s-compatible add-ons showed just 8 of the top 20 Firefox extensions: Notable conflicts included FireBug and NoScript Security Suite.

If all goes well with the initial seeding, the 1% will be expanded to all in the less-likely-to-have-problems group.

Only later this year, with Firefox 48 and Firefox 50 -- now slated to ship on Sept. 13 and Nov. 8, respectively -- will users running add-ons receive the multi-process browser. Firefox 51, with a release date of Jan. 24, 2017, will extend multi-process to users running touch-enabled devices, people who need the browser's accessibility features, and those on versions localized for right-to-left languages such as Hebrew and Arabic.

Firefox has been on the ropes in its fight to retain users. In the year's first seven months, Firefox shed a third of its user share. During July, however, Firefox rebounded slightly, regaining a bit more than one-tenth of a percentage point.

"This is a huge project that will take several more releases to complete," warned Asa Dotzler, the product manager in charge of the Firefox roadmap, referring to e10s. "But we've got a great foundation in place with the first phase shipping to end users now."

Firefox users can determine whether multi-process has been enabled by typing about:support in the address bar, then looking at the "Multiprocess Windows" entry.

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