I've asked Apple Developer Support, regular Apple Support, and high-level Apple Support. They all said to ask on the Apple Developer Support Forums. I figured I'd ask here as well because I have much better experience on SE.

I am a senior software engineer working on a Photos Extension. I have multiple machines on which I want to test my code. Photos requires that its Extensions operate through Projects. For instance, one might right-click an album and create a new Book or Calendar. Our Photos Extension properly uses the Photos and PhotosUI APIs to manipulate these projects, and Photos takes care of serializing our changes. I am developing Motif for multiple versions of macOS (High Sierra, Mojave, and Catalina). To do so, I have multiple Macs, each with a different OS installed on it.

One of the things that I want to fix is a problem that we see when upgrading from Mojave to Catalina. One way I could do this is to install macOS Mojave on one of the Macs, create a project, and then update that Mac to Catalina. This, however, is very time-consuming. Instead, I would like to create a project in Photos on a Mac running macOS Mojave, export that project (say, to a thumb drive), and import it into Photos on a Mac running macOS Catalina.

Since there is no UI for exporting a project, I want to know where these projects are stored in the filesystem. I intend to then copy those project files (say, via a thumb drive) between Macs in order to perform these tests. Could you please help me achieve this?

  • I didn't see anything in the main photos.db, so I'm not immediately sure. Is resources/projects/ also empty for you? – JMY1000 Oct 7 '19 at 15:26
  • resources/projects/ has a data/ directory with some .tiff caches of the project preview images, and an empty legacy/ folder – Ben Leggiero Oct 7 '19 at 17:11

Here is the official answer from Apple (specifically, Jack, a senior advisor with Apple Developer Program Support):

After reviewing both public and Apple Developer support documents, the most transparent answer I can provide here is that if these files were directly accessible and transferrable in the way that you are asking, that information would be documented. In reviewing our documentation, I found that all files and subsfolders associated with the Apple Photos app are packaged in the user>Pictures>Photos Library.photoslibrary file. As the structure and contents of this package are not defined in any Apple Support documentation, Apple Support will likely not be able to provide the specific answer you are looking for.


I've not yet found the precise location of each project, but I have found that it's stored in the photo library. So, to perform this transfer, I just zip up the library and transfer it over. Doing this I can also have multiple sets of projects to test with, and if I need to, I can revert to an older/primary/specific one at any time.

I would still like to just move/copy/backup just one project, but as of now this will be my kludge.

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