Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

How to stop multiprocessing being disabled on start?

  • 4 replies
  • 1 has this problem
  • 5 views
  • Last reply by cor-el

more options
  1. Summary

I am unable to enable multiprocessing. I tried enabling it by setting `browser.tabs.remote.autostart` to `true` in `about:config`. However whenever I quit and re-open the browser, that setting has been changed back to `false`. How can I get it to stay `true`?

  1. Details:
  • Firefox 64.0.2, 64 bit, Windows 7.
  • This computer is managed by my employer. However I installed Firefox myself, straight from mozilla.org.
  • `about:support` says `Multiprocess Windows 0/1 (Disabled)`. (Note that if an add-on is causing multiprocessing to be disabled, it will say "Disabled by Add-on", which is not what I'm seeing.)


  1. What I've tried:
  • I have disabled my addons.
  • I have looked for prefs.js and mozilla.cfg in the locations listed here: https://support.mozilla.org/en-US/questions/1237547 The only one which exists is `C:\Program Files\Mozilla Firefox\defaults\pref\pref.js`. I do not have sufficient permissions to modify or delete that. The contents seem unrelated:

``` /* This Source Code Form is subject to the terms of the Mozilla Public

* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

//pref("app.update.channel", "release"); ```

  • I went to `about:support`, clicked on "Profile Folder: Open Folder", (C:\Users\$USERNAME\ApPData\Roaming\Mozilla\Firefox\Profiles\$HEX.default`) searched for prefs.js in that folder. I quit firefox, changed the `browser.tabs.remote.autostart` setting there to true, saved, and started firefox again. The setting in `about:config` was false, and `about:support` shows multiprocessing is disabled.

Impact: I am not able to use the "responsive design" functionality. Also, the browser is quite slow. (I don't even have many tabs open, always < 15)

#Summary I am unable to enable multiprocessing. I tried enabling it by setting `browser.tabs.remote.autostart` to `true` in `about:config`. However whenever I quit and re-open the browser, that setting has been changed back to `false`. How can I get it to stay `true`? # Details: * Firefox 64.0.2, 64 bit, Windows 7. * This computer is managed by my employer. However I installed Firefox myself, straight from mozilla.org. * `about:support` says `Multiprocess Windows 0/1 (Disabled)`. (Note that if an add-on is causing multiprocessing to be disabled, it will say "Disabled by Add-on", which is not what I'm seeing.) # What I've tried: * I have disabled my addons. * I have looked for prefs.js and mozilla.cfg in the locations listed here: https://support.mozilla.org/en-US/questions/1237547 The only one which exists is `C:\Program Files\Mozilla Firefox\defaults\pref\pref.js`. I do not have sufficient permissions to modify or delete that. The contents seem unrelated: ``` /* This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ //pref("app.update.channel", "release"); ``` * I went to `about:support`, clicked on "Profile Folder: Open Folder", (C:\Users\$USERNAME\ApPData\Roaming\Mozilla\Firefox\Profiles\$HEX.default`) searched for prefs.js in that folder. I quit firefox, changed the `browser.tabs.remote.autostart` setting there to true, saved, and started firefox again. The setting in `about:config` was false, and `about:support` shows multiprocessing is disabled. Impact: I am not able to use the "responsive design" functionality. Also, the browser is quite slow. (I don't even have many tabs open, always < 15)

All Replies (4)

more options

I haven't checked recently, but usually in a new profile, the first run is "single process", then Firefox assesses the system and turns it on for future sessions. This shows up in about:config --

browser.tabs.remote.autostart.2 => true

The corresponding line in the prefs.js file is

user_pref("browser.tabs.remote.autostart.2", true);

Since yours seems to be intentionally disabled, could it due to something in the environment, maybe an environment variable?

more options

I have no `browser.tabs.remote.autostart.2` setting. It's missing from `about:config`.

None of the environment variables seem relevant. Only `NUMBER_OF_PROCESSORS=4`

more options

I found a solution:

I had to create 2 new boolean entries in `about:config`

   `browser.tabs.remote.force-enable` to false
   `browser.tabs.remote.autostart.2` to true 

That fixed it for me

more options

Current Firefox releases only support the main autostart pref.

  • browser.tabs.remote.autostart = false

The previously used opt-in pref browser.tabs.remote.autostart.2 is no longer supported in Firefox 58+.