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Firefox on macos starts on wrong Mission Control Desktop (a.k.a. Space)

Issue: When Firefox starts after a system reboot, it starts on the incorrect desktop. This seems to be off by one; that is, I have Firefox assigned to Desktop 3 (using … (read more)

Issue: When Firefox starts after a system reboot, it starts on the incorrect desktop. This seems to be off by one; that is, I have Firefox assigned to Desktop 3 (using the Dock icon's Options menu). Under normal operation, it starts on Desktop 3, but after a reboot, it seems to start on (more recently) Desktop 2 or (earlier) Desktop 4. Unsure about what causes it to prefer 2 vs. 4.

This seems to happen after I've shut down (quit Firefox normally, shut down without reopening windows on login, power goes off, power on, log in, then click on the Firefox icon in the Dock) or after a system update (which reopens windows on login for me after rebooting and installing the update). It does not seem to happen after a Firefox update or after quitting Firefox normally and then restarting it from the Dock icon right away.

Pretty irritating, as I have major applications assigned to specific desktops, and Firefox is the only one that seems to forget which desktop it should be on.

Details:

Firefox 150.0.3 (aarch64):

  • Settings > General > Startup > Open previous windows and tabs > TRUE (checked)

macos 26.5 (25F71) Tahoe:

  • Settings > Desktop and Dock > Mission Control:
  • ---> Automatically rearrange Spaces based on most recent use: FALSE
  • ---> ...switch to a Space with open windows for that application: TRUE
  • ---> Group windows by application: TRUE
  • ---> Displays have separate Spaces: TRUE
  • Dock > Firefox application icon > [Right Click] > Options > Assign To > This Desktop (i.e., Desktop 3)
  • Apple Menu > Shutdown > Reopen windows when logging in: FALSE

MacBook Air M4 2025 24 GB RAM:

  • No external displays connected
Open
Firefox Customization