I have about 8 photo libraries, all of them on a [connected and mounted] external disk. One of them is the System Photo Library, but which one? I have forgotten.

Since I upgraded to Big Sur, Photos.app is saying it cannot find the System Photo Library. Apparently, Photos.app is looking for it in some place where it is not.

I would like to know where it is looking, and what is the name of the library it is looking for, so that I can point it to its correct location.

Necessarily, Photos.app has this information stored somewhere. Where?

  • Try hitting the option key right after opening photos. It should display a menu to select the library you want to open. Maybe this helps.
    – X_841
    Nov 25, 2020 at 9:43
  • Yes but that doesn’t help: the one currently designated as the System Photo Library is not highlighted in any way Nov 26, 2020 at 17:31

1 Answer 1


In Photos if you go to preferences (⌘ + ,) under General there are some library location settings:

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In order to find out where System Photo Library is and to change it just hold ⌥ while opening Photos. You will be presented window with needed controls:

enter image description here

Refer to Apple documentation for needed steps: Designate a System Photo Library in Photos

  • That shows the last open library. Not the current System Photo Library. Your screenshot shows the current System Photo Library. I know because the “Use as...” button is grayed out. I tried opening all the photo libraries I could find, but that button was always enabled. So where the heck does Photos.app think the current System Photo Library is? Nov 26, 2020 at 17:34
  • I edited answer and provided link to Apple documentation. Nov 26, 2020 at 19:19
  • Thanks. But it still doesn’t help. I have 8 photo libraries in this list, and it doesn’t show which one is the current system one. As far as I can see, there is no exposed user interface to get that information. I am now hoping for a command line solution, perhaps with the ˋdefaultsˋ command Nov 27, 2020 at 23:14
  • I have only one library so I don't have this situation and I rely on claim made by Apple in linked support document: "Hold down the Option key when you open Photos to see which library is set as the System Photo Library.". Nov 27, 2020 at 23:24
  • Indeed the support article says that. But in my experience, this is not true. Nov 29, 2020 at 3:04

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