Thunderbird will use multiple processes in the future

If you are using the Nightly version of the Thunderbird email client, called Thunderbird Daily, then you may have noticed that recent versions of Thunderbird Daily use multiple processes. Stable and Beta versions of Thunderbird use a single process on the other hand.
Thunderbird, being based on code that Mozilla Firefox uses, will follow the Firefox web browser. Mozilla introduced support for a multi-processor architecture in Firefox in the year 2016 to improve the browser's stability. Downside to using multiple-processes is that the browser uses more memory. Google Chrome and all Chromium-based browsers have a multi-process architecture as well.
The first step towards a multi-process architecture has been made in Thunderbird Daily. The current implementation won't provide "noticeable improvements" for the foreseeable future, but it is the cornerstone that future improvements will build-on.
Thunderbird users won't notice changes when they upgrade to a Daily version that supports multiple-processes. Users may check the system's process manager to verify that Thunderbird uses multiple processes, but that is about it currently.
Thunderbird loads extensions in child processes, and will use processes for content that is loaded, e.g. the homepage or a new tab page or window.
Beta versions of Thunderbird may receive the update as early as next week, and Thunderbird Stable later in 2021, likely after the release of the next Thunderbird ESR version, version 91 in Summer.
Thunderbird users who don't want the email client to use a multi-process architecture may disable it in the following way for now:
- Select Tools > Options in Thunderbird. If you don't see the menu bar, tap on the Alt-key to display it.
- Scroll all the way down on the "General" page.
- Select the Config Editor button to open the advanced configuration editor.
- Confirm that you will be careful if a warning page is displayed.
- Search for the preference browser.tabs.remote.autostart and set it to FALSE.
- Search for the preference extensions.webextensions.remote and set it to FALSE. Doing so disables the multi-process architecture for installed extensions that are enabled.
- Restart the Thunderbird email client.
Thunderbird will go back to using a single process for the entire client.
Now You: What is your take on the integration? (via Sören Hentzschel)


You said that Outlook isn’t your main email client, so which is your main one?
I think its thunderbird
It is Mozilla Thunderbird.
Awesome! This actually solved my problem… what a stupid bug.
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.
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!!!!
Solved my issue! 6 years later and this is still problem…
Fantastic. Thank you. Size did the trick.
This solved my Outlook problem, too. Thank you. :)
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.
You are a god – thank you!
thanks a lot…. work like charm.. :-)
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
Excellent post. This had me baffled even trying to accurately describe the problem. This fixed it for me.
Thank you
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 :-)
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.
I’ve been tried to sole this problem for 12hours. Your comment about changing the display of screen helped me a lot!! Thanks!!
Thank you…don’t know why this happened but your instructions helped me fix it. Running Windows 10 and office pro 2007
Great tip! Thanks!
Worked for me, too – thank you!!!
It’s Worked for me, too
thank you very much!
I had a similar issue with Outlook 2013 on Windows 10 and this helped me to fix it. Thank you very much!
Thank you so much. Solved!
Considering you published this in 2012, incredible not been debugged by Microsoft.
Thank you again. M
This problem was faced by only one user logging to TS 2008 r2 using outlook 2010.The issue was resolved.
Thanks.
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.
Thank you, this worked !!!!
Man, you are a fucking god. Thanks a lot, what an annoying bug!!
Awesome, this post solved the issue. Many thanks!