Mozilla has published Firefox 48 and this new release contains one of the biggest changes to Firefox in a long time. This version is the first to implement Mozilla's Electrolysis project, which is the ongoing effort to finally add multi-process support to Firefox to enhance the browser's security and stability.
This doesn't mean everyone will get Electrolysis from the start. Mozilla will do a very slow rollout, to ensure no big problems pop up. At first, just 1 percent of the user base will get the feature enabled by default, and this should increase to about half of the userbase if things go well.
The browser maker is also still working on splitting each tab into its own content. At the moment, the first phase of Electrolysis includes splitting the UI and the content in a separate process. Per-tab processes are still some time away from us.
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.
If you've updated to Firefox 48, you can force the browser to enable Electrolysis via the following procedure, but some restrictions may still apply.
If you've tried enabling e10s but about:support indicates that e10s is disabled (e.g., accessibility, add-ons can trigger this), you can force e10s on for testing purposes. Within about:config create a new boolean pref named browser.tabs.remote.force-enable and set it to true. This is not encouraged, use it at your own risk!