Do this to fix Flash game lag issues in Firefox 49.0.2

Martin Brinkmann
Oct 25, 2016
Updated • Oct 26, 2016

Reports are coming in that the most recent version of the Mozilla Firefox web browser is not playing nicely with Flash game sites and games across the Internet.

Users are reporting all kinds of issues including extreme lag and rendering issues, that the mouse wheel stops working, the mouse cursor is lost, and that mouse clicks are delayed. Users are also reporting slow gameplay on Firefox 49.0.2 when they run Flash games in the browsers.

Mozilla enabled a new flag in Firefox that enabled asynchronous rendering for Flash in the new version of the web browser. It appears that this change is causing the issues that Firefox users are experiencing.  The issue seems to be causing issues predominantly on Windows machines.

Affected games include many Facebook games that rely on Flash like Farmville 2 but also site navigation and of course gaming on sites like

The issue is quite serious as gaming is a popular activity not only on social networking sites like Facebook but also elsewhere.

It appears that that some developers have already started to display banners asking users to switch browsers to resolve flash game lag issues.

The fix

firefox fix flash games lag

Firefox users who are experiencing issues playing Flash games in the web browser may do the following to correct the issue:

  1. Load about:config in the browser's address bar.
  2. Confirm that you will be careful if the warning prompt is displayed.
  3. Search for dom.ipc.plugins.asyncdrawing.enabled.
  4. Double-click the preference to set it to false.

This disables asynchronous rendering of Flash content in Firefox and should resolve the issue.

Mozilla's reaction

Mozilla plans to push a system add-on to Firefox 49.0.2 installations that disables the preference mentioned above. It will set the preference to false to correct the issue. It is unclear when the system add-on will be made available, but it could be as early as today.

It is likely that Mozilla will analyze the issues and try to correct them before enabling the preference again in the future.

One thing that is not that good is that the organization won't fix the bug for 64-bit versions of Firefox for Windows until Firefox 50 gets released. Mozilla plans to release Firefox 50 on November 8, 2016.

It seems strange that Mozilla won't fix the issue directly on 64-bit versions of Windows.

Now You: did you experience the issue in Firefox?

Do this to fix Flash game lag issues in Firefox 49.0.2
Article Name
Do this to fix Flash game lag issues in Firefox 49.0.2
Reports are coming in that the most recent version of the Mozilla Firefox web browser is not playing nicely with Flash game sites across the Internet.
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  1. TR said on December 10, 2016 at 5:19 am

    If anyone else is having this issue (lag when moving mouse with Flash in Firefox) I enabled this setting and it corrected the issue.

  2. Yip said on November 26, 2016 at 3:38 pm

    This still won’t work for me.
    I have to keep rolling back to 49.0.1 as 49.0.2 or 50.0 won’t play flash, all I get is a black screen.
    I guess I’ll put up with ignoring the notifications to update until a version is released that works for me :(

  3. Anonymous said on November 24, 2016 at 1:02 am

    Found the solution to my problem. Turned off uBlock Origin for that website. Works fine now.

    1. TR said on December 10, 2016 at 5:20 am

      Wish I would have tried this.

  4. MisterB said on November 15, 2016 at 4:29 am
    Reply no longer works with Firefox 49.0.2, but works fine with Chrome. I reckon it has something to with Flash and I’ve tried a few things without success. Any fix?

    1. MisterB said on November 24, 2016 at 1:05 am

      Found the solution… I turned off uBlock Origin.

  5. King Chop Chop said on October 31, 2016 at 10:49 pm

    That fix worked great, Thank you :)

    Now I can continue my quest in destroying castles on Empire

  6. Anonymous said on October 27, 2016 at 12:53 am

    “The fix” worked great. TY

  7. MAGILLA CEO said on October 26, 2016 at 7:20 pm

    Honestly, is anyone wondering why any new and improved version from MOZILLA CORP. gives errors and problems?

    Really are you still hanging to a hog of a spyware browser?

    How much time will you waste on such CORPORATE GREED?

    1. Nafus said on October 26, 2016 at 9:33 pm

      And your recommendation is ………?

    2. Parker Lewis said on October 26, 2016 at 8:01 pm

      Wow, that convinced me to switch to Microsoft’s browser at work and to one of the Chromium derivatives littered with Google’s source code contributions at home.

      Thanks for opening my mind! The corporate greed and spyware arguments really hit the spot.

  8. Tom said on October 26, 2016 at 4:45 pm

    on firefox 50b10 this is set to false by default. well, at least in the x86 version, i’m not using firefox x64.

    and please, let flash die finally. i wouldn’t mind to see it go, but i’m afraid it will still be around by 2020… :(

  9. Tom Hawack said on October 26, 2016 at 12:59 pm

    Setting dom.ipc.plugins.asyncdrawing.enabled to false had resolved (partially) the lag issue. That was for Adobe Flash Player ver.

    Adobe Flash Player has just been released. Once installed I tested Flash with dom.ipc.plugins.asyncdrawing.enabled set to true, again, to see if the lag issue had been resolved. Nops. So back to dom.ipc.plugins.asyncdrawing.enabled set to false.

    Tested on Firefox 49.0.2 64-BIT / Windows 7 64-BIT

    EDIT- As I understand by reading comments, the issue would be that of Mozilla Firefox on 64-BIT builds and not that of Adobe’s Flash- OK

  10. Sören Hentzschel said on October 26, 2016 at 11:24 am

    > It seems strange that Mozilla won’t fix the issue directly on 64-bit versions of Windows.

    Not really, because async plugin rendering fixes serious regressions with the 64-bit version of Firefox for Windows, the 32-bit version is not affected. It’s also explained in Bugzilla:

    > For win32, we can disable async rendering with this system add-on/hotfix; For win64 there are bigger code changes, so we’d need to ship a full release to fix async rendering/plugin drawing.

  11. Gary said on October 26, 2016 at 9:14 am

    No, I’m sure he meant 2011 as we all know Firefox is just building a corn maze and as the autumn of their seasons approaches they will die along with their maze. I’ll just be sadly forced to move on.

    1. Anonymous said on October 26, 2016 at 10:36 am

      Just tried Chromium Portable with Flash PPAPI and AdditionalParameters= –disable-infobars in the .ini. Very fast and all is working better particularly Ublock Origin. I will keep it until they fix the whole thing.

  12. Doc said on October 26, 2016 at 6:47 am

    “Mozilla plans to release Firefox 50 on November 8, 2011.”

    Wow, does it include a flux capacitor? LOL…I think you meant “2016.”

  13. city_zen said on October 26, 2016 at 4:05 am

    GHacks is rendering differently on mobile, did you make any changes to the website? I usually read GHacks through Flipboard, and the content used to be displayed like a “modified” version of the website. But the comments for each article were fortunately visible, since I often find the comments very useful too. But now, both on Flipboard and on every mobile browser I have on my phone (Opera, Firefox and Chrome), the content of GHacks is rendered differently and the comments for each article are no longer visible. I had to load GHacks on my desktop PC to be able to post this comment.

    1. Martin Brinkmann said on October 26, 2016 at 6:00 am

      Hi, I’m testing a new version of a mobile theme currently and yes, in its current form, it does not support comments. I will look into it though.

  14. Jon Wold said on October 26, 2016 at 1:24 am

    Just a little typo you might want to fix:

    “Mozilla plans to release Firefox 50 on November 8, 2011.”

  15. Anonymous said on October 25, 2016 at 11:26 pm

    I really wonder for what exactly all their fu-(ing telemetry is used !!!

  16. Mark Hazard said on October 25, 2016 at 11:23 pm

    Thanks, Martin.

  17. Anonymous said on October 25, 2016 at 11:13 pm

    Like with Windows 10 for Microsoft users/customers became alpha/beta testers, from Mozilla Firefox users are now considered in the same way… not even capable to make correct tests before releasing “updates” ! And yes Flash is always alive and we need it functional as much as possible.

    1. Mikhoul said on October 26, 2016 at 6:35 am

      All Major News websites around the world (like BBC, TVA etc…) that use Flash player for their Video just show you a white or black video with sound.

      Mozilla is trying to match Micro$oft on the Amateurism level on Quality Control.

  18. CMON NOW said on October 25, 2016 at 10:32 pm

    Flash games are obnoxious in modern IT and play against everyone’s Enterpreneurship.

    I suggest you to login to STEAM and buy a legitimate GAME there.

    Flash gaming is not fair in today’s capitalistic standards.

    Just abandon item.

    1. Sledge said on October 29, 2016 at 1:26 am

      How should I say this…
      Millions of people play flash games all around the web. Steam has tons of crappy games that cost money to boot. Digital Homicide, there’s a fine, outstanding example of what we should spend our money on.
      In all seriousness,
      for the people who don’t have the hardware capabilities to run the latest “AAA” games, arkham knight or bloodborne or whatever,
      flash games are objectively better.
      You don’t seem like you know jack about flash games, so please shut your trap and stop trying to provoke people.
      That’s all your comment seems to be really-
      A grab for saltiness.

    2. Doc said on October 26, 2016 at 6:46 am

      Um, no.
      Don’t tell me what to do.

      1. ReviewTechUSA said on October 27, 2016 at 3:01 pm

        That’s the wrong thing to say.Flash is not old.

      2. Anonymous said on October 26, 2016 at 8:29 pm

        Ditto, Doc.

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