Firefox 48 began rolling out to users yesterday. This major update marks the beginnings of a fundamental change to the way Firefox processes work: it splits the browser into a process for its user interface and a process for the web content it's displaying. This change is the first mainstream release of the work from Mozilla's Electrolysis project, whose labor is meant to make Firefox less crashy while improving its responsiveness and security. Developer Aza Dotzler calls this release "the largest change we've ever shipped."
Electrolysis won't be rolling out to every user with Firefox 48. Mozilla is only turning on the feature for users that aren't on Windows XP and without extensions, screen readers, or right-to-left languages enabled. Of those eligible users, only 1% of them will get a browser with Electrolysis on by default at first. If no major problems crop up, Mozilla will then turn on Electrolysis for all eligible Firefox 48 users, or about 50% of the user base, according to the company.
Mozilla also outlined its plan for Electrolysis and the next few versions of Firefox. The company says that Firefox 49 will begin deploying the feature for users with a small list of pre-approved add-ons. Firefox 50 will expand Electrolysis to folks using add-ons with a compatibility flag set or for add-ons built with Mozilla's WebExtensions framework. Firefox 51 will enable Electrolysis for those with screen readers and right-to-left languages. The company says that release will mark the conclusion of the first major phase of the Electrolysis rollout. Future versions of Electrolysis will split each tab into its own content process. Mozilla expects the fruits of that labor to become available in the first half of next year.
As someone who's had Firefox crash and hang regularly thanks to problems with rogue plug-ins or tabs, I can only say "full speed ahead." Electrolysis is enabled in Firefox 48 on my Mac, and I haven't noticed any instability or weirdness that I'd attribute to the new feature. I'm hopeful that this improved architecture will help Firefox regain some popularity in the browser market. Going by NetMarketShare's latest numbers, all versions of Firefox account for 8.1% of the browser market, ahead of Microsoft's Edge but behind all versions of Internet Explorer and dwarfed by Google Chrome's 51% share.
If you're curious whether you have Electrolysis enabled, enter "about:support" in the Firefox address bar and look to see whether "Multi-process staged rollout" has a Boolean value of "true" in the Extensions table.