I have a mid-2014 15-inch MacBook Pro (the one with the Retina display) with macOS 10.12.6. I use spaces a lot and normally have my most-used apps open in specific spaces. One of these is Safari, which is set to always open in space 2 (out of 5). However, I often move Safari windows to different spaces as needed (for instance, if I'm going to use a website for reference while using an app that runs on space 4, I'll move the window with that website to space 4).

I tend to leave Safari open when I turn my computer off; that way, I get back any windows and tabs which I was using in my last session and am likely to use again in my next session. However, when the computer starts up, sometimes some of the windows which were in different spaces go back to space 2. It doesn't happen always, and when it happens it only happens with some windows (so, for example, the window on space 1 will remain there but the windows on spaces 3-5 will have migrated to space 2).

(I know that quitting Safari and reopening it causes all windows to go to the space where it's opened or where it's told to open in. I'm talking about Safari restarting by itself again after I've shut down or restarted the computer without having quit Safari, which normally puts windows in the spaces they were in before the computer was shut down or restarted.)

Does anyone know why this happens?

1 Answer 1


The only thing that is supported is 'one app, one Space'.
Once you spread an app to more than one Space, results will be at best random.

I would have expected that any relaunch, whether after reboot or not, would reduce your content to a single Space. I'm actually surprised it sometimes doesn't.

  • Yeah, I'm surprised too, hence my question. Randomness and computers don't (or shouldn't) really go together, so my guess is there's something behind the "randomness"; I'd like to know what.
    – Rain
    Oct 6, 2017 at 15:41
  • I come back to this question periodically - but I have to say that on Mojave I cannot repro the 'intermittent' issue at all. No matter where or how I spread windows to Spaces, after a relaunch, they will always pile up in one Space.
    – Tetsujin
    Jul 1, 2021 at 9:31
  • Hi! Are you leaving Safari open when you shut down and having the computer reopen apps and windows automatically upon restart? Or are you quitting Safari manually?
    – Rain
    Jul 1, 2021 at 9:48
  • Either/or, makes no difference. I've also tried setting affinity to a single Space vs none - again no difference.
    – Tetsujin
    Jul 1, 2021 at 11:19

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