Mozilla Thunderbird 12 Slow? Try This Fix!

Martin Brinkmann
May 9, 2012
Updated • Aug 28, 2013
Email, Thunderbird

If you are using Mozilla's Thunderbird email client on a desktop computer, you probably have updated to version 12 of the client when the new version came out. Shortly thereafter, Thunderbird was updated to version 12.0.1, which resolved several issues that came to light after the final release of Thunderbird 12.

Some Thunderbird users ever since they have updated to Thunderbird 12 have noticed that the client's performance dropped considerably. This is for instance the case when affected users open emails in the program, as it may happen that it takes longer than usual to do so. Thunderbird in some instances may even freeze, for a while.


According to Mozilla, the most likely cause for this is antivirus software running on the system. Bugs have been filed by users running NOD32 and Avira Antivir, with the likelihood that other antivirus applications may cause the issues as well.

A workaround has been posted to fix the issue for affected users.

  • Open the Thunderbird Profile Directory from Help | Troubleshooting Information
  • Quit Thunderbird
  • Delete any directories in the Thunderbird Profile Directory ending in "-wal" or "-shm"
  • Then restart Thunderbird
  • E.g. delete directories named like the following: "places.sqlite-wal", "places.sqlite-shm", "cookies.sqlite-shm", "cookies.sqlite-wal"

Users need to make sure that they only delete directories, and not files in the Thunderbird profile folder to test the fix. I'd suggest to make a backup of the profile folder - with Thunderbird closed- to avoid any issues that could result from this. MozBackup can do that for instance.

Once you have deleted the folders in the Thunderbird profile directory, restart Thunderbird to see if the issue has been resolved.

According to Mozilla, a patch for the issue is in the making to resolve it on their side of things. You find the full bug report listing here, in case you are interested or want to share your own experience. (thanks Sören)

Update: Please note that this fix only works for the issue described above. Thunderbird does not use these directories by default, which is why you probably won't find them listed in the client profile directory when you open it.

You can check out our guide on fixing a slow or hanging Thunderbird client for general tips to improve its speed or resolve the issue that you are experiencing when using it.


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  1. jrc said on February 12, 2014 at 5:02 pm

    Typical Mozilla straight-arm for problems with new versions of FF and TB. “Oh, it’s somebody else’s (enter name of software here) fault.” Visions of the constant problems with Adobe Flash and Firefox – a lot of finger pointing and no real resolution. Conclusion: Mozilla considers itself ‘above’ fixing inconvenient problems it overlooked – or ignored – when rewriting THEIR software. Old hat response from software ‘engineers’: “Blame it on somebody else.”

    BTW – New FF is also slow. For the record, I have no new AV software. Therefore, the problems occurred when, and because of, the installation of newer versions of FF and TB. And you wonder why we are so reluctant to ‘upgrade’.

  2. wobbly.jim said on March 27, 2013 at 5:10 am


    Directories do not have “file” extensions, so the following is not possible :
    “Delete any directories in the Thunderbird Profile Directory ending in “-wal” or “-shm””

    “E.g. delete directories named like the following: “places.sqlite-wal”, “places.sqlite-shm”, “cookies.sqlite-shm”, “cookies.sqlite-wal””

    Files do have file extensions, but FILE deletion is not advised:
    “E.g. delete directories named like the following: “places.sqlite-wal”, “places.sqlite-shm”, “cookies.sqlite-shm”, “cookies.sqlite-wal””

    So, what is the real solution ?

    Thnx, James

    1. Martin Brinkmann said on March 27, 2013 at 5:23 am

      As noted by Mozilla: Thunderbird 12.0.1 very slow when opening a message / not responding due to Thunderbird Places SQLite “*-wal and *-shm” files (and possibly other TB SQLite files) being removed and replaced with a directory

      So, these are directories in this case.

  3. Mike said on May 27, 2012 at 5:27 pm

    This is terrific fix – I was pulling my hair for a couple of weeks trying to figure out what was wrong.

  4. Rich said on May 22, 2012 at 4:27 am

    This helped!!! Thanks!!

  5. Gindy said on May 16, 2012 at 8:04 am

    I am a competent silver-surfer and I had terrible problems with long delays, but this simple solution has worked like a dream – many thanks.

  6. Jonathan said on May 9, 2012 at 6:22 pm

    I’m having an issue with TB taking a long time to fetch the messages from the servers, I access via IMAP, and oftern have to wait a min or more just a message to load. I checked the profile directory and there are not any of the listed files. Could this be the server issue or ISP?

  7. Ken Saunders said on May 9, 2012 at 1:40 pm

    I haven’t noticed any issues, but I appreciate the info none the less.
    I wonder if it’s because I download emails at startup and use POP instead of IMAP?
    They’re also downloaded while I’m doing other things like using Firefox or other software, or, getting a snack. :)

    You sure stay on top of things.
    That’s why this is one of my top sites to follow.

    I sincerely appreciate the work that you all do and the service that Ghacks provides.

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