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Going forward, Multi-process can't be turned off anymore in Firefox

Mozilla plans to remove configuration options in upcoming versions of the Firefox web browser that allow users to disable the browser’s multi-process architecture.

Mozilla introduced the multi-process architecture in the Firefox web browser in 2016. Firefox would use multiple processes to divide loaded sites between them and use different processes for the browser’s own functionality.

While that increased memory usage, it also meant that Firefox would become more stable in the process and less prone to site crashes taking the entire browser with them. Mozilla’s implementation was different to Google’s. Chrome uses one process per site, Firefox puts multiples sites in a single process.

Firefox’s Multi-process architecture received numerous improvements over the years. Mozilla added more processes to it and introduced a sandbox security feature later on that depended on it.

firefox multi process cant disable

Mozilla plans to remove two Firefox preferences from any version of the web browser going forward. The change is planed for Firefox 68.

  • browser.tabs.remote.force-enable — Enforces the use of multi-process in Firefox if it is not enabled by default, e.g. because of accessibility.
  • browser.tabs.remote.force-disable — Disables multi-process in the Firefox web browser.

You probably wonder about browser.tabs.remote.autostart, the preference that enables or disables the multi-process architecture in Firefox (opposed to enforcing a value like the two other preferences do).

Mozilla will restrict the preference to true in home builds. While it is still in Firefox, setting it to false in about:config won’t have the desired effect anymore once the change lands. The status of the preference is always true in home builds of Firefox regardless of the user chosen value.

In other words: going forward, Firefox users can’t disable multi-process anymore in the browser. It is unclear in how many Firefox installations multi-process is disabled. Some users do so to improve memory usage or slowness of the browser.

Closing Words

Mozilla does not reveal why it wants to remove the preference on Bugzilla, only that disabling multi-process should not be “that easy”. Additional information is available in a post on the Mozilla Dev Platform group:

The broad aim was to ensure that we stop grandfathering users into a non-e10s configuration which they
should not run on a day-to-day basis, given that it receives little to no testing and is less secure.

It was mentioned as well that Activity Stream breaks if multi-process is disabled. (via Techdows)

I’m not particularly fond of changes that remove user choice from any program including web browsers. Mozilla is probably going to get a lot of flak for the removal even if it affects only a minority of users of the browser.

Firefox 68 is the next ESR release of the browser. It is scheduled for a July 9th, 2019 release.

Now You: What is your take on the change?

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