How to enable electrolysis (e10s) on Mozilla Firefox Beta

In about:config (see http://kb.mozillazine.org/About:config to learn how to use "about:config")

Set browser.tabs.remote.autostart to true

On your next restart, e10s should be active. To verify that it is active, go to about:support and look for a number higher than 0 in "Multiprocess Windows".

To summarize it:

In the address bar, write about:config, answer yes to the warning, search for variables line after line, and set the values to those after equal sign:

browser.tabs.remote.autostart=true

extensions.e10sBloc­kedByAddons=false

extensions.e10sBloc­ksEnabling=false

Create a variable (or key for those who think of this as some kind of registry) with a boolean value (Right click in the pane with search results, Select "new"): browser.tabs.remote.force-enable=true

Restart the browser, then go to about:support and as @gagarine mentioned, in Multiprocess Windows, there should be "1/1 (user activated)".

Update:

Now in Firefox 54, you should have Electrolysis on by default. You should check out the option dom.ipc.processCount and if it is still 1, turn it higher to match the physical core count, or if you know you use hyperthreading (most Core i7 and i3 on desktop, most Core i5 and i7 in laptops, AMD Ryzen), it is double that. (You can also see that in Task Manager under performance on Windows and in top or cat /proc/cpuinfo | grep processor on Linux).

Read more about it here: https://medium.com/mozilla-tech/the-search-for-the-goldilocks-browser-and-why-firefox-may-be-just-right-for-you-1f520506aa35

Mine shows "0/1 (Disabled by add-ons)". It seems some accessibility options may disable this feature.

According to Mozilla Wiki, you can force it to enable in these cases by also adding browser.tabs.remote.force-enable on about:config and setting it to true, but it also alerts it may break something.