362      iPhone_iPad_Mac_apple

Photos uploading library again after restoring ...

I restored my MacBook Pro after installing a new hard drive. The backup included the downloaded copies of my photo library. Upon launching Photos, it is now uploading the entire photo library... again!

I verified the original iCloud photo library is fine, I just don't want the system to churn away trying to upload copies. No copies actually appear, so I assume it verifies it's a copy and doesn't add it. All I can do is pause it for a day, but it just picks up where it left off.

Has anyone else encountered this behaviour?

Welcome to the Apple Community.

You'll need to let it complete, the more you pause the longer it will take. As you say it's checking for duplicates, it won't actually start adding the photos a second time, but it may take a while to complete.

Photos will upload the library again, for several reasons, if you copy the Photos Library to a different drive, if you restore the library from a backup, or if you simply repair the library.

You can see what kind of upload and download is being done in the Console window, but not the names of the image files:

Open the Console.app (it is in Applications > Utilities). The Console will show you, what iCloud is doing. Type "cloudphotosd" into the search field:

When the library is uploaded again, I am mostly seeing entries of duplicate checks. Like Winston Churchill stated, this will usually not result in duplicates being added, but it can result in plenty of network traffic.

The "Duplicate detection" messages will look like this in the Console window:

I'm experiencing the same thing. I had to replace my hard drive so I had to restore onto a new drive. Now iCloud Photo Library is uploading my whole library again.

I hope that is not what it is actually doing. It seems insane to upload them all (100GB worth) just to check if they are duplicates. Surely there is a better way with checksums on the image or something? All this because of a restore??

It is just comparing to make sure everything is uploaded.

Eric, I wish Apple would document more precisely, what Photos is actually doing, when we are seeing the "uploading" message after we restored a library, moved it to a different drive, or repaired the library.

So far, I only have found one support document, that mentions this new upload - see the last sentence:

https://support.apple.com/en-us/HT205069

Note: If you use iCloud Photo Library with Photos, this action will cause Photos to re-upload all your pictures.