User profile for user: tprusaczyk
tprusaczyk Author
User level: Level 1
1 points

iCloud Photos syncing slowly on Mac with large library

iCloud Photo sync takes ages.


My system: MacMini 2024 - M4

MacOS Tahoe 26.1

Internet: 600Mbps ( around 500Mbps where the computer is placed )


Some background info: this library ( further details below) was constantly synced with my iPhone, so the local and the iCloud library are pretty much the same.


I changed my Photo library ( previously local ) to be the system library and synced to iCloud.


I have around 60K photos and around 1K videos in this library.


The local file ( backup before the change ) was almost 800Gb.


I see now it is syncing with iCloud and I would say it is doing on a rate of 1 photo per minute on average.


My internet is not slow 600Mbps ( it almost hits this number where the computer is, around 500mbps ).


I understand the complexities ( sort of ) of the Photo library, it has files, folders, etc, but this is ridiculously slow.


I see posts from 3 .. 4 years back with same issue. Is there someone from Apple to comment on this topic?


I know this is how it is at the moment and there's no solution to speed it up, so the question I more an attempt to get something from Apple. I definitely am not the only user with this issue.


Thanks


Mac mini, macOS 26.1

Posted on Dec 2, 2025 2:27 AM

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User profile for user: azaksalmarzur28
azaksalmarzur28
User level: Level 2
426 points

Posted on Dec 2, 2025 5:29 PM

iCloud Photos does NOT upload raw photo/video files directly

Before each item can upload, Photos must:

  1. Parse and rebuild the internal database (very CPU-intensive)
  2. Generate thumbnails and previews
  3. Extract metadata (faces, scenes, objects, memories)
  4. Apply duplicate detection
  5. Match items with existing iCloud entries
  6. (especially important when the same library existed previously on your iPhone)
  7. Encrypt the data client-side (end-to-end)
  8. Even without ADP, Photos encrypts sensitive metadata.
  9. Upload with throttling to avoid choking system resources


How to speed it up significantly:


1. Leave the Mac awake

Set:

System Settings → Displays → Display Sleep → Never

and

System Settings → Energy → Prevent sleep when display is off

Photos uploading stops or slows drastically when the Mac sleeps.


✅ 2. Quit Photos and leave it closed

This surprises many users:

📌 Uploading is faster when Photos is closed.

The Photos window constantly updating thumbnails slows processing.


✅ 3. Keep the Mac plugged in & cool

The Photos database rebuild stresses CPU and SSD.

If it overheats, throttling begins → slow sync.

✅ 4. Ensure "Optimize Mac Storage" is OFF

Otherwise Photos will download from iCloud while trying to upload, slowing everything.

Go to:

Photos → Settings → iCloud → Optimize Mac Storage → OFF

✅ 5. Make sure iCloud has enough free storage

Large library + videos + indexing = temporary overhead files.

Keep 15–20% free space in iCloud.


✅ 6. Do NOT import or edit while syncing

Any modification forces re-rendering and restarts indexing queues.

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Question marked as Top-ranking reply
User profile for user: azaksalmarzur28
azaksalmarzur28
User level: Level 2
426 points

Dec 2, 2025 5:29 PM in response to tprusaczyk

iCloud Photos does NOT upload raw photo/video files directly

Before each item can upload, Photos must:

  1. Parse and rebuild the internal database (very CPU-intensive)
  2. Generate thumbnails and previews
  3. Extract metadata (faces, scenes, objects, memories)
  4. Apply duplicate detection
  5. Match items with existing iCloud entries
  6. (especially important when the same library existed previously on your iPhone)
  7. Encrypt the data client-side (end-to-end)
  8. Even without ADP, Photos encrypts sensitive metadata.
  9. Upload with throttling to avoid choking system resources


How to speed it up significantly:


1. Leave the Mac awake

Set:

System Settings → Displays → Display Sleep → Never

and

System Settings → Energy → Prevent sleep when display is off

Photos uploading stops or slows drastically when the Mac sleeps.


✅ 2. Quit Photos and leave it closed

This surprises many users:

📌 Uploading is faster when Photos is closed.

The Photos window constantly updating thumbnails slows processing.


✅ 3. Keep the Mac plugged in & cool

The Photos database rebuild stresses CPU and SSD.

If it overheats, throttling begins → slow sync.

✅ 4. Ensure "Optimize Mac Storage" is OFF

Otherwise Photos will download from iCloud while trying to upload, slowing everything.

Go to:

Photos → Settings → iCloud → Optimize Mac Storage → OFF

✅ 5. Make sure iCloud has enough free storage

Large library + videos + indexing = temporary overhead files.

Keep 15–20% free space in iCloud.


✅ 6. Do NOT import or edit while syncing

Any modification forces re-rendering and restarts indexing queues.

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User profile for user: Richard.Taylor
Richard.Taylor
User level: Level 6
16,909 points

Dec 2, 2025 10:00 AM in response to tprusaczyk

People from Apple are not here (except for moderators who aren't involved with content.) We are a Community of users.


My System Library has about 20,000 favorite pictures, and I don't really experience super-slow syncing. If I edit pictures, that shows up very quickly. When I add a bunch of pictures, it may take a couple of hours, especially if I'm using the computer. Photos doesn't want to slow down my work, so it will delay syncing until my computer is not so busy-- particularly until Photos is not active. The times I'm meaning are between my transferring pictures to Photos and when they show up on my iPad.


When it's important to transfer an image with my iPad quickly, I use AirDrop.

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iCloud Photos syncing slowly on Mac with large library

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