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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:

1. Select Tools > Options in Thunderbird. If you don't see the menu bar, tap on the Alt-key to display it.
   
2. Scroll all the way down on the "General" page.
   
3. Select the Config Editor button to open the advanced configuration editor.
   
4. Confirm that you will be careful if a warning page is displayed.
   
5. Search for the preference browser.tabs.remote.autostart and set it to FALSE.
   
6. 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.
   
7. 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?
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