Firefox 48 for Windows, Mac and Linux has been officially released and available for download. Mozilla has planned to ship Multiprocess Windows (e10s) to one percent of eligible users who have no extensions installed, to check your Mozilla browser after installing Firefox 48 has e10s enabled or not and know how to enable it if Multiprocess Windows was disabled for you.
Visit about:support, if e10s turned on for you, you’ll see ‘ 1/1 (Enabled by default), under Multiprocess Windows line item,, if not you’ll see ‘0/1 (Disabled)‘, this will be the case for most of the users.
If e10s is disabled for your Firefox, don’t worry! you can still enable it manually,
Manually enabling e10s in Firefox 48 if disabled by default
1. Visit about:config and set browser.tabs.remote.autostart preference value to true. If it was already set to true, no need to make any changes.
2. Now create a new boolean preference named ‘browser.tabs.remote.force-enable’ and set its value to true. if you’ve any accessibility tools installed, change accessibility.force_disabled preference value to
false 1 from 0.
Now restart the browser, visit about:support, you’ll notice 1/1 (Enabled by User) for Multiprocess Windows line item.
Hope that helps.