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Why does Photos upload all your photos again when you migrate from one Mac to another?

I got a new MacBook Pro a few days ago and used a Time Machine backup to migrate my apps and documents from my old MacBook Pro to the new one. I'm curious why Photos is going through the process of uploading all the photos in my Photos Library. It's taken over 24 hours and is about ⅓ of the way through. All those photos are already up in my Photos Library in iCloud. Why does Photos go through the lengthy process of uploading them again?

MacBook Pro with Touch Bar

Posted on May 22, 2020 4:13 PM

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Posted on May 23, 2020 9:14 AM

It actually isn't uploading but just comparing like you mentioned. It still is a lengthy process as it has to read each photo entry in the local library, search for the same photo in the iCloud library and read all of its data and then compare.. Repairing the library by opening it with the Option+Command keys held down will trigger the same "recertification" of the library.


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Question marked as Top-ranking reply

May 23, 2020 9:14 AM in response to Daniel Voran

It actually isn't uploading but just comparing like you mentioned. It still is a lengthy process as it has to read each photo entry in the local library, search for the same photo in the iCloud library and read all of its data and then compare.. Repairing the library by opening it with the Option+Command keys held down will trigger the same "recertification" of the library.


May 22, 2020 6:42 PM in response to Daniel Voran

As far as iCloud Photos Library is concerned, you just added a new Library. In order to ensure all your (potentially) new images are copied to iCloud, it uploads them to compare to what’s already stored. Yes, it’s a very slow process, leave your MacBook powered overnight. This should not result in creating duplicates.

May 22, 2020 8:06 PM in response to Rysz

That seems to be what is happening, but it doesn't make sense. When you set up a new MacBook, the process knows you are migrating from another system, so it knows that this is not a new Photo Library, but one that you have just copied from another Mac. So why doesn't it do a quick check to see if the name, date, and size of the photos is the same? It could do that check quickly, instead of going through the process of uploading, in my case, 18 years of photos, when all those photos are already in iCloud. It's a huge waste of system and bandwidth resources.

Why does Photos upload all your photos again when you migrate from one Mac to another?

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