How To Force Extension Compatibility In Thunderbird

Martin Brinkmann
Jan 23, 2011
Updated • Jan 10, 2015
Email, Thunderbird

You may know that I made the switch to a new version of Thunderbird some time ago which is currently available as an alpha release. Most of the extensions available for Thunderbird are not compatible with this version.

I never really bothered to find a solution for that since I did not make use of must-use extensions in the email client. It was however bothersome to run an earlier version of the email software side-by-side to test extensions.

I decided to investigate the issue to find a way to force compatibility in Thunderbird. The following guide should help all Thunderbird users who need to make an extension compatible.

I know of three methods to force compatibility in Firefox and since the programs share the same core it felt natural to begin there.

The best working method after some tests is in my opinion to override compatibility enforcement in the email client's configuration. This is done the following way:

Start Thunderbird and open the configuration window by clicking on Tools > Options first. This opens the options window. Go to Advanced > General and click on the Config Editor button there.

thunderbird config editor

The config editor opens in a new window. The directive does not exist by default which means that it needs to be added first. The general format of the parameter looks the following way:


The version is always separated with a dot, e.g. 3.3. If Thunderbird is a release version that's all that needs to be added. Alpha and beta versions on the other hand need to be specified individually by adding an a for alpha or b for beta behind the version.

The compatibility parameter for Thunderbird 3.3 alpha 2 is therefore


To add it right-click in the configuration window and select New > Boolean from the list. A form pops up. enter the parameter name, e.g. extensions.checkCompatibility.3.3a and click ok. Now you need to select if the Boolean value should be true or false. True in this case is the default value which means that Thunderbird will check for extension compatibility. Since we do not want that we set the value to false. Restart the email client and install your extensions. Inactive extensions that have been inactivated because of incompatibilities should show up as activated.

thunderbird compatibility

And this is the result in the extension listing

add-on compatibility checking

Please note that forcing compatibility is no guarantee that the extension will actually work in Thunderbird. It is helpful if an extension developer has not updated the extension yet that is otherwise compatible with the version of Thunderbird.

You need to understand as well that the parameter that you have just configured needs to be adjusted whenever the version of the email client changes.

Update: The majority of tips outlined below work in newer versions of Thunderbird as well. In addition, you can also install the Disable Add-on Compatibility Checks extension for the email client for that as well now. It automates the process so that you don't have to change the version of the parameter each time the program updates to a new version.

How To Force Extension Compatibility In Thunderbird
Article Name
How To Force Extension Compatibility In Thunderbird
Find out how to force compatibility for extensions that stopped working after you have upgraded the Thunderbird email client to a new version.

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  1. JMGG said on January 19, 2012 at 8:25 am

    You said that Outlook isn’t your main email client, so which is your main one?

    1. BalaC said on January 19, 2012 at 9:42 am

      I think its thunderbird

    2. Martin Brinkmann said on January 19, 2012 at 10:15 am

      It is Mozilla Thunderbird.

  2. Salaam said on September 24, 2012 at 9:52 pm

    Awesome! This actually solved my problem… what a stupid bug.

  3. Claud said on December 19, 2012 at 2:08 am

    If this is the same bug that I’ve encountered, there may be another fix: (1) hover over open Outlook item in Taskbar, cursor up to hover over Outlook window item, and right-click; (2) this should give you Restore / Move / Size / Minimize / Maximize — choose Move or Size; (3) use your cursor keys, going arbitrarily N/S/E/W, to try to move or size the Outlook window back into view. Basically, the app behaves as though it were open in a 0x0 window, or at a location that’s offscreen, and this will frequently work to resize and/or move the window. Don’t forget to close while resized/moved, so that Outlook remembers the size/position for next time.

    1. Lynda said on February 12, 2013 at 3:37 pm

      THANK YOU Claude!!! I could get the main window to launch but could not get any other message window to show on the desktop. You are my hero!!!!

    2. Chad said on November 20, 2018 at 4:24 pm

      Solved my issue! 6 years later and this is still problem…

    3. Ivan X said on January 21, 2021 at 4:50 pm

      Fantastic. Thank you. Size did the trick.

  4. Andrew said on October 26, 2013 at 7:06 am

    This solved my Outlook problem, too. Thank you. :)

  5. Charles said on December 7, 2013 at 7:23 pm

    Thank you so much, this started happening to me today and was causing big problems. You are a life saver, I hope I can help you in some way some day.

  6. garth said on November 7, 2014 at 7:13 pm

    You are a god – thank you!

  7. Faisal said on February 9, 2015 at 10:09 am

    thanks a lot…. work like charm.. :-)

  8. Simon said on March 24, 2015 at 11:36 pm

    Yah…thanks Claude. I’ve been having the same problem and tried all the suggestions…your solution was the answer. It had resized itself to a 0/0 box. Cheers

  9. Olu said on April 14, 2015 at 1:35 pm

    Excellent post. This had me baffled even trying to accurately describe the problem. This fixed it for me.
    Thank you

  10. Coenig said on July 23, 2015 at 7:36 am

    Thanks a lot for the article. Don’t know why it happenend, don’t know how it got fixed, but it was really annoying and now it works :-)

  11. Fali said on January 20, 2016 at 4:19 pm

    Thanks a lot. I was facing this issue from past 3 week. I tried everything but no resolution. The issue was happening intermittently and mainly when I was changing the display of screen ( as i use 2 monitors). The only option i had was to do system restore. But thanks to you.

    1. MIki said on January 10, 2019 at 11:54 am

      I’ve been tried to sole this problem for 12hours. Your comment about changing the display of screen helped me a lot!! Thanks!!

  12. Christina said on January 20, 2016 at 6:14 pm

    Thank you…don’t know why this happened but your instructions helped me fix it. Running Windows 10 and office pro 2007

  13. Oz said on July 22, 2016 at 3:20 pm

    Great tip! Thanks!

  14. Tracy said on September 1, 2016 at 4:48 pm

    Worked for me, too – thank you!!!

  15. shawn said on September 9, 2016 at 10:25 am

    It’s Worked for me, too
    thank you very much!

  16. Jari said on October 31, 2016 at 11:53 am

    I had a similar issue with Outlook 2013 on Windows 10 and this helped me to fix it. Thank you very much!

  17. Michel H said on November 30, 2016 at 11:08 pm

    Thank you so much. Solved!
    Considering you published this in 2012, incredible not been debugged by Microsoft.
    Thank you again. M

  18. Ziad Bitar said on January 9, 2017 at 2:00 am

    This problem was faced by only one user logging to TS 2008 r2 using outlook 2010.The issue was resolved.


  19. Anonymous said on February 15, 2017 at 5:24 pm

    Great tip. Thank you!!!! If it helps, I had to use the Control Key and the arrow keys at the same time to bring my window back into view. Worked like a charm.

  20. Rochelle said on March 6, 2017 at 11:59 am

    Thank you, this worked !!!!

  21. anom1234 said on May 20, 2018 at 11:20 pm

    Man, you are a fucking god. Thanks a lot, what an annoying bug!!

  22. JC said on October 12, 2020 at 2:14 pm

    Awesome, this post solved the issue. Many thanks!

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