Firefox Tip: turn off accessibility services to improve performance

Firefox users who are experiencing performance issues while using the Firefox web browser on desktop systems and on Android, may improve performance by disabling the browser's accessibility services.

A bug opened on [email protected] four days ago suggests that Firefox's Accessibility Service has a memory leak that is causing performance degradation, especially on heavy webpages.

To make matters worse, Mozilla did remove options to control the desktop browser's accessibility settings from the preferences some time ago. While it is still possible to turn them off using about:config, it is probably not something that most users know about or feel comfortable using.

Reports suggest that some users managed to reduce the Firefox web browser's memory usage after disabling the service; others on the other hand reported that changing the setting did not impact memory usage. It may be a good idea to test this on the local system to find out if the local Firefox installation is affected by the issue.

Note: Accessibility Services may be required for assistive software, extensions and other tools. These may stop working if the feature is disabled in the Firefox web browser.

It is unclear how widespread the bug is, and whether it is linked to something else; this would explain why disabling the service works only for some Firefox users and not all. Mozilla is investigating the issue.

Find out if Accessibility Services are enabled

firefox accessibility services

To find out if Firefox's Accessibility Services are enabled, do the following:

  1. Load about:support in the browser's address bar.
  2. Scroll down to the Accessibility section near the end of the page.
  3. If you see Activated false, the service is disabled. If you see true, the service is enabled.

Disable Accessibility Services

firefox accessibility turn off

If you are using the desktop version of the Firefox web browser, or Firefox Nightly for Android, do the following to turn of the browser's Accessibility Services:

  1. Load about:config in the browser's address bar.
  2. Continue when the warning page is displayed.
  3. Use the search field to find accessibility.force_disabled.
  4. Change the value of the preference to 1 (default is 0). On the desktop, double-click on the line and edit it.
  5. Restart Firefox.

The setting disables the feature forcefully in the Firefox web browser. You may reset it to its default value of 0 at any point in time to restore the functionality.

On Android, disabling the text sizing feature in settings has a similar effect.

Now You: did you try the fix? What was the outcome?

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Firefox Tip: turn off accessibility services to improve performance
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Firefox Tip: turn off accessibility services to improve performance
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Firefox users who are experiencing performance issues while using the Firefox web browser on desktop systems and on Android, may improve performance by disabling the browser's accessibility services.
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Comments

  1. Kenny said on August 25, 2021 at 4:10 pm
    Reply

    Thanks for the useful tip. I can always count on Ghacks with the latest.

  2. James Cone said on August 25, 2021 at 4:21 pm
    Reply

    Using 64 bit Windows 10.
    Accessibility | Activated was already set to False on Firefox 88.0.1

    I didnt do nuffin to it.

    1. Beta said on August 30, 2021 at 7:42 pm
      Reply

      Same here, but I had to set “accessibility.force_disabled” to “1”

  3. Tom Hawack said on August 25, 2021 at 6:57 pm
    Reply

    I’ve always had accessibility.force_disabled set to 1 (disabled)
    I have no ‘Accessibility’ section in about:support, the only occurrence appears in ‘Important Modified Preferences’

    No performance degradation ever noticed, latest FF 91.0.2 included.
    What is excessive memory consumption? At start (personal homepage, no other tabs) Task Manager just reported 452 196 KB. Hardware acceleration is on, Content process limit is 8 (default).
    Start is always initiated after cache cleanup.
    [https://img.justpaste.me/i/20210825/mIvyU/1.png]

    Memory degradation over time and number of opened tabs is another scheme. No idea really given I never have more than 8 tabs opened, usually. I never tried opening hundreds of tabs as I’ve read some do. Not even dozens. I’d get lost!

  4. sunnytimes said on August 25, 2021 at 7:34 pm
    Reply

    on android the browser became lightning fast after disabling .. on desktop i haven’t noticed a difference , it was already plenty fast.

  5. VioletMoon said on August 25, 2021 at 8:19 pm
    Reply

    Martin, danke; eine Einstellung, die ich komplett übersehen hätte. FF war für mich in den letzten zwei Monaten schrecklich instabil, also was auch immer helfen kann.

  6. Yash said on August 25, 2021 at 10:41 pm
    Reply

    Haven’t tried it on desktop as I haven’t updated Firefox yet, but in Android since version 91, Firefox has become laggy which reminds of Chromium browsers. Accessibility is already set to 1 so it is related to new update. Given Firefox’s track record, fix is on the way hopefully in next version update. No issue on Nightly which is on version 93 so it will be solved soon on stable Firefox.

  7. TomG said on August 26, 2021 at 12:54 am
    Reply

    Sadly no changes in the abnormal ram usage by Firefox even with accessibility turned off. Nearly the triple of Edge and Chrome…
    The same in Ubuntu… also compared with Edge and Chrome.
    Firefox only works “normally” on secure mode but they don’t care. Appearance is more important.

    1. Yash said on August 26, 2021 at 7:52 am
      Reply

      Did you really said Ubuntu? I use Firefox in Ubuntu and can confirm loading time, performance and all that is better in Firefox than Chrome or any other Chromium browser. Loading is worse in Chromium browsers, sometimes takes even 5 min for browser to open, same for performance which is why I only use Firefox which is better in all regards.

      1. Nico said on August 26, 2021 at 11:56 am
        Reply

        @Yash
        Firefox is my main browser, but loading time of Chromium on Linux Mint (based on Ubuntu) is ~1sec. (i5; SSD; 16GB RAM).
        So something else must be interfering with your Chromium…

      2. Yash said on August 26, 2021 at 10:14 pm
        Reply

        Same setup but with 8GB RAM, normally when I switch on desktop, it seems Chrome is taking forever to load, sometimes even 5 min, most of the time more than 3 min. In comparison Firefox takes maybe 25-35 seconds for profile manager to open and another 15 seconds for tabs to appear. I wouldn’t say my desktop doesn’t need a reset and wipe data, but comparing Firefox and Chromium as of now, Chromium does take time.

    2. VioletMoon said on August 26, 2021 at 7:19 pm
      Reply

      Yes, I’m still using Firemin version 8 to help with the FF RAM issue, knowingly aware of new issues that arise with its use.

    3. TomG said on August 26, 2021 at 8:03 pm
      Reply

      Retested now in Ubuntu with latest version and disabling accessibility reduced memory usage by around 40%…
      Still more than Chromium browsers but at least can use it again without the system having to use the swap file.

  8. Dennis said on August 26, 2021 at 7:41 am
    Reply

    This preference is set as disabled by default in the arkenfox user.js…

    https://github.com/arkenfox/user.js

  9. TelV said on August 26, 2021 at 3:07 pm
    Reply

    Activated is set to False, but Accessible Handler Used shows “True”.

    Also, Prevent Accessibility is set to 0.

    FF version 91.0.2

  10. Anonymous said on September 7, 2021 at 11:45 am
    Reply

    “To make matters worse, Mozilla did remove options to control the desktop browser’s accessibility settings from the preferences some time ago. While it is still possible to turn them off using about:config, it is probably not something that most users know about or feel comfortable using.”

    What is making me uncomfortable here is that I had not even noticed the change before reading it here. Mozilla did not mention it in release notes (they often hide worse and bigger changes than that). I had not added the pref in my user.js because I thought I could change it through UI for new installs but I would have simply forgotten that the checkbox existed !

    This means that from now on one should either check at every update every pref to see which ones disappeared from the UI, or preventively completely stop using the UI and only use the user.js equivalents…

    Mozilla never stops finding new ways to harm.

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