How do you find which photos are in one Photos library but not in another on a Mac?

By Kayabyte · Last updated 11 November 2026

Short answer: Photos shows one library at a time, so by hand you open each library in turn and look (checked 11 November 2026 against Apple’s page on moving your Photos library: quit Photos, hold Option while opening it, pick the library and click Choose Library). We know of no side-by-side compare in Photos itself. AlbumRescue’s Compare lists what one library has that another does not, and what differs, without opening either library. The comparison is free. It only reads.

When you need this

You have an old library and a new one and want to know what did not make it across.
A library was repaired or migrated and looks smaller than expected.
You restored a library from a backup and want to see what the backup lacked.

The manual way

Quit Photos, hold Option while opening it, choose the first library and note the counts and the albums.
Quit again, open the second library the same way and note the same things.
Compare by eye: album names, number of items, a few photos you know.

Opening a library in Photos can change it, so work on copies if either one matters. Apple’s page also says that if Photos can’t find a library on an external drive, it creates a new empty library in the Pictures folder, so connect the drive before you open Photos. Counting by eye does not tell you which individual photos are missing.

With AlbumRescue

AlbumRescue reads a Photos library on an external drive, from an old Mac, in a damaged copy or in a Time Machine backup. Its Compare view shows what this library has that another one does not, and what differs. Next to it, the Overview says what is really on the disk, and Missing or Limited lists each item with no full original in that copy, and why.

Some things it can’t see. Originals that stayed in iCloud under Optimize Mac Storage are not in the copy, so they show as limited. Edits are not exported. Shared albums, iPhoto libraries and libraries from macOS 10.14 or earlier are not supported. A Time Machine copy has no People names we could verify. It does not write into Photos and never opens or changes the library.

Steps with AlbumRescue

Open AlbumRescue and allow Full Disk Access, or click Choose a Library for a library on an external drive.
Scan the first library, then the second.
Open Compare and pick the other library.
Read what one has that the other lacks, and check Missing or Limited before you trust a count.
To keep what is missing, choose Export: folders that follow your albums, with a sidecar .xmp file per photo and a CSV report. A free sample saves 5 photos.

The scan, lists, comparison and 5 saved photos are free. The full export is USD 34 once, for 2 Macs. macOS 15 or later.

Download AlbumRescue and scan for free

Questions

Does Compare change either library? No. It reads a private copy of the database.

Can it put the missing photos back into Photos? No. It does not write into Photos. It saves them as files in folders.

Does it need both libraries on the Mac? It reads a library wherever you can point it: a drive, a folder copied from a library, an old Mac’s library or a Time Machine backup.

Apple, Mac, macOS, iCloud and Time Machine are trademarks of Apple Inc. AlbumRescue is made by Kayabyte and is not affiliated with or endorsed by Apple.