Problem with initial sync of mac photo library to icloud photos

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Problem with initial sync of mac photo library to icloud photos

I have my full library of photos/videos on my mac which comprise photos/videos i have taken with various cameras and with my iPhone (i upload most of the iPhone images to my mac). Since i was running out of storage on the iphone i decided to use iCloud photos. The plan was to upload my iPhone images to the cloud and then optimise storage on this device which i did and all seemed fine with around 400GB of images in the cloud from my iPhone.

I decided to upload my macs photo library as well to have an additional copy. I had more than 300GB of free space on my mac so i presumed that i would have enough space to accommodate the already uploaded iPhone photos as they would just be duplicates i had uploaded already to my mac. The plan was still to keep the originals on the mac. When i clicked iCloud photos to begin the upload it automatically changed the selection to optimise storage so i changed it back to download originals. When i checked on progress the next morning i noted that my disc scanner said i now had 1.7TB of photos on my mac having started with 900GB but paradoxically while i started with 55000 odd photos on my mac, the photos library now said i had less than 40,000. I repeated my disk scan using daisy disc later on and it said i now had only 700+ GB in my photo library. I wondered whether the optimise storage had proceeded anyway. So i deselected the iCloud photos setting on my mac to see if i could figure out what was going on. When i turned it back on i received a warning that my full sized originals would not fit on my mac and i would need to optimize storage. This was not my plan so i did not proceed with this. I disconnected the internet for a few yours and on reselecting iCloud photos in my mac photo settings I again selected download originals to my mac. The photos app says i have 38,724 photos, 7429 videos and it is syncing 54566 items to the cloud. The photos library itself is apparently now 1.75 tb.

I am now left with a couple of issues. Does my mac photo library now have a mixture of optimised and full sized images (and how would i determine this) and why is the photo count significantly lower than before. And going forward should i continue to try to keep originals on the mac (i have cleared some additional space so this might be an option) or should i choose what iCloud seems to have preferred and and just go the optimise photos on mac route (I could later try again to download originals on my mac).

If anyone can see a good way forward here and maybe explain what is happening I would love to hear !

Thnx for any input.

Kind Regards

Andrew M

iMac 24″, macOS 15.5

Posted on Oct 11, 2025 2:01 AM

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Answer 1

Top-ranking reply

Richard.Taylor

Level 6

16,327 points

Oct 11, 2025 8:35 AM in response to andrewfromsorrento

When a Library is connected to iCloud Photos, Photos does what's needed to merge the Libraries without removing pictures or leaving duplicates. It will eliminate exact duplicates, but it leaves pictures that have any differences.

Download Originals is the only reliable way you can make timely backups of your stuff. I use Optimize on my iPhone, but not on my primary Mac. Since you have a desktop Mac, you can consider putting your Photos Library on a fast external drive. Spotlight won't search there, but that's a small inconvenience. Otherwise it works fine. Be sure the drive is formatted APFS!

If you've had "Optimize" checked, then you can't be absolutely sure that all your originals are downloaded after switching to "Download Originals." Photos loads the originals as needed. You may be able to select pictures and attempt to print to pdf-- I think it downloads the files before printing, so you could stop the process after the download. The trusted 3rd party app PowerPhotos ($40) can be useful in identifying optimized picture files.

You could create a new empty Photos Library, make it your System Library, connect it to iCloud, and wait a couple of weeks (?) for it to fill with pristine copies of your pictures.

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Answer 2

Oct 11, 2025 3:16 PM in response to Richard.Taylor

Hi Richard,

Thnx so much for your reply. I have a new SSD coming and think i will follow your advice and use it to store my photos library as there is no way it seems to fit all my photos on my mac’s SSD.

Having stopped the iCloud sync I am wondering what happened to the some of my mac photos - the photo count on my mac is down from around 55000 to less than 40000. Might these be in the cloud (although the cloud photos count is not too much different they might have been recognised as duplicates from my iPhone’s library and potentially not bump up the iCloud count) or might they be gone forever ? I realise now that stopping the sync was not a good idea and might have created problems.

Thnx for any insights.

Andrew

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Answer 3

Oct 12, 2025 6:52 AM in response to andrewfromsorrento

andrewfromsorrento wrote: … Having stopped the iCloud sync I am wondering what happened to the some of my mac photos - the photo count on my mac is down from around 55000 to less than 40000.

It hard to know from here. It could be duplicates. When pictures are synchronized between a device and iCloud, Photos does its best to not copy duplicates. But it only affects exact duplicates, never pictures that just look the same.

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