Ghost windows on macOS

[wolruf]

Hello,

Running Firefox 145.0.2 on macOS 26.1 (issue existed before for months, years) with two displays.

After some time, some ghost windows exist when displaying all apps on macOS.

These windows cannot be accessed via Firefox Window menu. Such windows go away when restarting Firefox.

Similar to this discussion, though on Windows https://connect.mozilla.org/t5/discussions/persistent-ghost-tabs-appear-on-windows-taskbar-with-dual...

[jack66james]

This sounds like the classic multi-monitor glitch on macOS. Ghost windows usually disappear after a restart, which suggests Firefox isn’t fully clearing background windows. Try disabling extensions or hardware acceleration to see if it helps. Hopefully, a future update will fix it completely.

[WashtubHumorles]

I'm having the same issue on my MacBook with macOS 13.1 and Firefox 145.0.2.

I'm only using the built-in display. These phantom windows appear in almost every session and always have the title of a recently closed window. They disappear when I restart Firefox.

[namakpara]

Hi @wolruf 

I’ve run into similar behavior on macOS when Firefox has been running for long sessions, especially with multiple monitors attached. In many cases the “ghost windows” seem to be orphaned UI processes that remain registered with macOS Mission Control but are no longer tied to an active Firefox window instance. That’s why they appear during the App Exposé view but don’t show up in the Firefox Window menu.

From my testing, this usually happens after:

• connecting or disconnecting a second display
• using Full Screen mode and then switching desktops
• long browsing sessions with many restored tabs

Refreshing the window state (restarting Firefox) clears them because Firefox reinitializes the window management layer on launch.

If useful for debugging, you can check Activity Monitor for any extra Firefox GPU or WindowServer-related subprocesses when the ghost windows appear. It may also help to try disabling hardware acceleration temporarily to see if the issue is related to rendering contexts not being released.

This definitely feels similar to the Windows case you linked, except on macOS it seems tied more to Mission Control’s window indexing. Hopefully Firefox’s window lifecycle handling on macOS can be tightened so these orphaned entries don’t persist after a window is closed.