Photos library too big on your Mac? How to shrink it

See how big the library is

The library is at ~/Pictures/Photos Library.photoslibrary. Select it in Finder and choose File, then Get Info, to see its size. The Storage screen in System Settings also shows a Photos row.

The command below prints the size of every Photos library in your Pictures folder. It only reads. If it lists more than one, you may have an old library from a previous Mac or an earlier import, which is worth knowing before you do anything else.

du -sh ~/Pictures/*.photoslibrary 2>/dev/null

Turn on Optimize Mac Storage

If you use iCloud Photos, open Photos, choose Settings, then iCloud, and select Optimize Mac Storage. The full-size originals stay in iCloud, and the Mac replaces them with smaller versions when it needs room. An original is downloaded again when you open or edit that photo.

This is the largest saving for most people, with two conditions. You need enough iCloud storage for the whole library, and you need a connection to open a full-size original. The library does not shrink immediately: macOS swaps originals for smaller versions gradually, as space gets short.

Keep in mind what iCloud Photos is. It keeps every device the same. If you delete a photo on the Mac, it is deleted from iCloud and from your iPhone as well. It is not a way to archive photos off your devices.

Empty Recently Deleted

Photos you delete are kept for 30 days in the Recently Deleted album, and they keep using space the whole time. In Photos, open Recently Deleted in the sidebar, unlock it if asked, and click Delete All.

This is permanent. Look through the album first, and recover anything you removed by mistake.

Merge duplicates and remove large videos

Photos finds exact and near duplicates on its own. If it has found any, a Duplicates album appears in the sidebar under Utilities. Open it and click Merge on each set, or select several sets and merge them together. Merging keeps the best version and combines the details, then moves the others to Recently Deleted.

Video takes far more space than photos. In the sidebar, open Media Types, then Videos, and look for long recordings you do not need: screen recordings, accidental clips, footage you have already edited into something else. Slow-motion and high-resolution video are the heaviest.

If you want to keep a video but not in the library, choose File, then Export, then Export Unmodified Original, save it to an external drive, check that it plays, and then delete it from Photos. After any of these, empty Recently Deleted to get the space back.

Move the whole library to an external drive

When the library is simply larger than the Mac can hold, move it. Use a drive formatted as APFS or Mac OS Extended, and one that is fast enough to browse comfortably.

• Quit Photos.
• Drag Photos Library.photoslibrary from Pictures to the external drive and wait for the copy to finish.
• Hold the Option key while opening Photos, and choose the library on the external drive.
• If you use iCloud Photos, open Photos Settings, then General, and click Use as System Photo Library.
• Check that the moved library opens and that recent and old photos are all there. Only then move the original in Pictures to the Trash.

What to know before relying on an external library

Photos can only open the library while the drive is connected. If it is not, Photos asks you to choose or create a library. Do not create a new one by accident. Connect the drive and try again.

A library that lives on a single external drive is one accident away from being lost. Make sure that drive is included in your Time Machine backup, or that iCloud Photos holds the originals.

What not to do

Do not right-click the library, choose Show Package Contents and delete folders inside. The folders are tied to a database, and removing files behind its back leaves you with missing photos and a library that needs repair.

Do not delete a second library you find in Pictures until you have opened it, by holding Option while starting Photos, and confirmed that everything in it also exists elsewhere.

Where Diskzy fits

Diskzy shows how large the library is on its map of the disk, next to everything else, which tells you whether Photos is really the problem or whether something else is larger. Managing what is inside the library is a job for the Photos app, and Diskzy leaves it to Photos.