Sequoia: 400 GB free storage but not really: How to force Photos to downsize using large encrypted disk images

I read Eclectic Light so I know about macOS APFS free space chaos. Recently macOS Photos quietly grew to consume most of my boot drive leaving only 30GB free. I switched to optimized storage while preserving a full local library on an external drive.

So Finder showed 400GB free --- but it's "purgeable free". So not really. One of my sparse disk image ran out of space (causing cryptic error messages) because it couldn't grow even 10GB.

In theory the OS should be shrinking the Photos Library as needed. But if it's doing that it's doing it slowly. An ai claims iOS Photos is much better at shrinking than macOS Photos; macOS Photos optimizes only under severe pressure (10GB free?!) and then only slowly.

I created sets of 20GB images followed by a shutdown and restart. Over an hour or so of this I was able to get 90GB truly free. That's enough free I can just chip away at the rest by creating then eventually deleting larger disk images (regular, NOT sparse). Just make sure you don't back them up accidentally - wastes space. A full shutdown appears to be needed as part of the routine (magical incantation).

(The other approach is to nuke local photos and let it rebuild optimized from iCloud.)

PS. There are so many bugs in modern Apple software I only post workarounds for the big ones. I will be glad to see Tim Cook retire.

Update 11/25/26

Some further refinements

• Create a folder to hold the disk image and in Time Machine set as no backup
• Use Disk Utility to see the real free space
• Create an encrypted (reduce compression possibility) disk image about 8-10 GB less than true free space. (If you make it too large Photos can't iCloud sync, about 8-10GB seems to work)
• Let things sit for a few hours.
• Shut down and restart
• Delete image and empty trash
• Shut down and restart and check Disk Utility for true free space
• Repeat every few days until Photos is beaten back
• Pray Tim Cook has a happy retirement

Once Photos starts optimizing it seems to work in bursts, sometimes freeing up 5-10GB in a burst of activity. Photos doesn't need to be running; folklore says it is faster if it's not running but I have not verified that. The full shutdown does seem to be necessary to see true recovered space. You can run Photos to verify that it's doing iCloud sync.

It's funny to see the different size estimates in Finder vs Storage (preferences) vs Disk Utility. In Storage Photos uses 35GB (aspirational!). In Finder it used 512GB originally, now down to 467GB and shrinking. Disk Utility showed about 15 GB free space, Storage says about 500 GB free, Finder Info says 500GB purgeable. 

macOS Photos: Optimized Storage version and External Drive Full Resolution version of same library

If your full resolution iPhotos Library won't fit on your internal drive any more you can switch to optimized storage. Even for a large library that's only 30GB or so [1], But they you can't do true backups with full resolution images. I like to have 5-6 full res backups rotated amongst drivers and servers including Time Machine.

The trick is to have two macOS user accounts with the same Apple ID [2]. One you use strictly for backup.

This is what I did starting with my Library in full res mode on my primary account. It takes about 610GB or so.

1. Copy Library to external drive.
2. Change primary Library to optimized storage [1].
3. Create new user account called iCloudBackup.
4. Log into iCloudBackup using same Apple ID as primary account. Turn off every iCloud feature.
5. Open full-resolution Library on external drive and make it the system library.
6. From within Photos turn on iCloud Photos support and set to full image download.
7. Keep the iCloudBackup account active for a few days so all sync things settle out. Then shut down.

Backups now have to include the external drive of course. You need to set something up so you periodically launch the full storage account and let it sync things up.

PS. You can track sync activity using nsurlsessionid network traffic in activity monitor.

PPS. You think -- "but now I'll be using a lot of extra backup storage". Because I'll backup my full res library in addition to the primary library which is still full res until storage pressure causes a purge. Ahh, but APFS is weirder than you know. [1]

- fn -

[1] In Optimized Storage my library is 30GB or so with optimizes storage enabled. In reality it's about 610FB  but that will shrink over time as needed. In Sequoia Finder says my backup of the 610GB is about 1GB in size, but on opening with network access disabled it contains all the data. I believe that's the chaos in file size problem with Sequoia -- the 1GB is because of deduplication at the APFS level, a single APFS container holds two Library backups, one "optimized" but only minimally purged at this time, the other non-optimized. Both over 600GB, but together they use about 601GB since the contents are so similar.

[2] I forgot that was allowed -- two accounts with same Apple ID. Kudos Claude 4.5 for the plan.

Update 11/10/25: After 5 days the optimized library is 90GB smaller than the full library. The optimized library SSD was short of storage so I expect the optimized to slowly shrink over time.

How to remove the "Live Photo" video from a macOS Photos.app image: Duplicate

As of Sequoia's end when you duplicate an image in Photos you have the option to "Duplicate as Still Photo" thus omitting the live image video.

So duplicate and delete original to remove video portion.