To move your Photos library to an external drive, quit Photos, drag the library from your Pictures folder to a drive formatted as APFS or Mac OS Extended (Journaled), and open it from its new place. Apple documents exactly these steps, and they move everything at once: originals, edits, albums, people and memories.
If you use iCloud Photos, there's one more step: make the moved library your System Photo Library again, in Photos › Settings › General. Then turn iCloud Photos back on in the iCloud pane. Only after you've checked the new copy do you drag the old library to the Trash and empty it.
The drive has to be one Apple supports for a library. That rules out your Time Machine drive, SD cards, USB flash drives, network drives and cloud folders. And it has to be connected and turned on every time you open Photos, or Photos starts a new, empty library instead.
The rest of this post covers what to check before you start, how to tell the copy worked, the choice iCloud Photos gives you, and how to fix the problems people run into afterwards.
Before you move the Photos library
A library move is a large copy of something you can't replace. Ten minutes of checks first saves hours of untangling later.
How big is your library, and how big a drive do you need?
Open your Pictures folder in Finder, select Photos Library, and choose File › Get Info. The size there is what the drive must hold today. Libraries range widely, from a few gigabytes to several hundred, and video makes up most of the large ones.
Leave room to grow. A library only gets bigger as you add photos, and if you use iCloud Photos and later choose Download Originals to this Mac, it grows to the full size of your iCloud collection. A drive at least twice the library's current size is a comfortable start.
Which drives can hold a Photos library?
Apple's instructions name two formats, APFS and Mac OS Extended (Journaled), and list the places a library must never live. Here's the whole picture in one table.
| Drive | Can hold the library? | Why |
|---|---|---|
| External SSD or hard drive, APFS | Yes | Apple's first choice for Macs |
| External drive, Mac OS Extended (Journaled) | Yes | Also supported; common on older hard drives |
| The drive you use for Time Machine | No | Apple says the library's permissions can conflict with the backup's |
| SD card or USB flash drive | No | Removable media, which Apple warns risks data loss |
| Network drive, NAS or cloud folder | No | Apple warns against anything shared over a network or the internet |
| ExFAT or MS-DOS (FAT) drive | No, until erased | Not formatted for Mac, so the needed permissions setting is missing |
To check a drive's format, select it in Finder and choose File › Get Info. The format is listed under General Information.
How do you format a drive for the library?
Erasing removes everything on the drive, so copy anything you need off it first. Then, in Finder, Control-click the drive in the sidebar, choose Erase Disk, choose APFS and click Erase. Apple documents this in macOS 26 Tahoe and macOS 27 Golden Gate; Disk Utility's Erase button does the same in any version.
APFS suits SSDs best. For an older spinning hard drive, Mac OS Extended (Journaled) is also fine, and Apple supports both for a library.
SSD or hard drive?
Either works, as long as it's formatted for Mac. An SSD has no moving parts, so it's faster to browse a large library on, quieter, and less likely to be hurt by a knock in a bag.
A spinning hard drive costs less for each terabyte and comes in larger sizes. It suits a library that's mostly an archive you open now and then. If you scroll and edit every day, the SSD's speed is easier to live with.
Whichever you choose, buy one with room for both the library and its growth. Running a library drive nearly full brings back the same problem you moved it to escape.
Check for referenced files before you move
Photos can leave imported files where they were and point to them, instead of copying them into the library. Apple calls these referenced files, and they matter here because they don't move with the library.
If yours are in Pictures or Downloads on your Mac, they stay there after the move, and so does the space they use. To check, select a few older photos and open the File menu. If Show Referenced File in Finder is available rather than dimmed, the selected photo is referenced.
To bring them into the library first, select them and choose File › Consolidate, then click Copy. Apple suggests this anyway, because referenced files aren't backed up with the library.
Back up before you start
Apple says to keep a local backup of your library even if you use iCloud Photos. Before a move, that advice matters twice: you're about to copy something large and then delete the original.
A recent Time Machine backup of your Mac covers it. If you don't use Time Machine, Apple's other method is to drag the library to a second drive to make a copy, which also tells you how long the real move will take.
How to move the Photos library to an external drive
These are Apple's steps, with the checks that make them safe. They're the same in macOS 27 Golden Gate and macOS 26 Tahoe. On versions before macOS Ventura, Photos › Settings is called Photos › Preferences.
Moving the library, step by step
- Connect the drive and make sure it appears in the Finder sidebar.
- Quit Photos.
- In Finder, choose Go › Home, then open Pictures, where Photos Library lives by default.
- Drag Photos Library onto the external drive. Because the drive is a different disk, Finder copies the library and leaves the original in place.
- Wait for the copy to finish completely. Don't put the Mac to sleep or unplug the drive while it runs.
- Double-click Photos Library in its new place on the drive. Photos opens it.
- If you use iCloud Photos, or want other apps' photo pickers to see this library, choose Photos › Settings, click General, and click Use as System Photo Library.
- Look through the library before you delete anything, as described below.
Where is your library, if it isn't in Pictures?
Open Photos, choose Photos › Settings, and click General. Under Library Location, Show in Finder opens the folder that holds the library in use.
If you have more than one library, quit Photos and hold the Option key as you open it. The Choose Library dialog lists the libraries Photos knows about. If yours isn't listed, click Other Library and find it in Finder.
How long does copying the library take?
It depends on the library's size, the drive and the connection. A library is thousands of files, many of them small previews, so a copy runs slower than the drive's headline speed. A large library over a slow connection can take hours.
- USB 2, 480 Mb/s55.6 minutes
- USB 3, 10 Gb/s2.7 minutes
- Thunderbolt 4 or USB 4, 40 Gb/s0.7 minutes
- Thunderbolt 5, 120 Gb/s0.2 minutes
Arithmetic from the maximum port speeds in Apple's specifications for current Macs. Real copies take much longer: the drive's own speed and the library's many small files set the pace.
Use the drive's own cable or one rated for data. Apple's USB-C Charge Cable, for one, carries data at only USB 2 speed, which turns a short copy into a long one.
A worked example
Say your Mac has a 256 GB disk and your library is 180 GB, mostly video, without iCloud Photos. You buy a 1 TB SSD, erase it as APFS, and drag the library across.
When the copy finishes, the drive holds 180 GB and the Mac still holds the original. Nothing is freed yet. You open the copy, check the oldest and newest photos and a few long videos, and use it for two days.
Then you drag the original to the Trash and empty it. About 180 GB comes back on the Mac. The drive still has more than 800 GB free, enough for years of new photos and a few finished projects.
How do you know the copy worked?
Don't rely on matching sizes: the copy's size in Get Info can differ a little from the original's, and that alone doesn't mean anything is wrong. Open the library on the drive and check what you'd miss most.
- Scroll to the start and end of Library, and check that the oldest and newest photos are there.
- Open a few albums, including ones in folders, and a few People entries.
- Play a long video and open a photo you edited, to see that the edit is still there.
- If you use iCloud Photos, check the status at the bottom of Library, under All Photos.
When is it safe to delete the original library?
Once the library on the drive has opened, you've looked through it, and you've used it for a day or two without problems. Then drag the original Photos Library from Pictures to the Trash and empty the Trash. The space comes back only when the Trash is empty.
Make sure you're deleting the one in Pictures, not the one on the drive. If you're unsure which is which, use Show in Finder in Photos › Settings › General while Photos has the drive's library open.
Moving the library with iCloud Photos on
iCloud Photos syncs only one library on a Mac: the System Photo Library. The moved copy isn't the System Photo Library until you say so, which is why Apple's steps include designating it.
What happens when you click Use as System Photo Library?
Apple says switching the System Photo Library turns off iCloud Photos and Shared Albums. Turn them on again in the iCloud pane of Photos › Settings.
When you do, Photos merges what's in iCloud with what's in the library. For a library you've moved, they're the same photos, which is why Apple's own move instructions include this step. Give Photos time to finish before you judge the result; for a large library, checking everything against iCloud can take a while.
Why you shouldn't designate a different library by mistake
The merge can't be undone. Apple warns that once a new System Photo Library's content is uploaded to iCloud, the libraries can't be unmerged. If you choose an old or unrelated library by accident, its photos join your iCloud library and appear on every device.
So check the library's name and location in Photos › Settings › General before you click Use as System Photo Library.
Download Originals or Optimize Mac Storage on an external drive?
Once the library has the room of a large drive, you get to choose again. Apple describes the two options this way:
| Setting | What the library on the drive holds | What it means for backups |
|---|---|---|
| Download Originals to this Mac | Full-size originals of everything, as well as in iCloud | A local backup of the drive holds every original |
| Optimize Mac Storage | Smaller versions when space is limited; originals in iCloud | Apple notes Time Machine may not have your originals |
Many people move the library precisely so they can keep every original locally. If that's you, choose Download Originals to this Mac, and expect the library to grow to the size of your iCloud collection as it downloads.
Another route: start a new library from iCloud
If your current library is optimized and everything is already in iCloud, you don't have to copy it. You can create a new library on the drive and let iCloud fill it.
- Check that uploads have finished: in Photos, click Library, then All Photos, and look at the status at the bottom.
- Quit Photos, hold Option as you open it, and click Create New. Choose a place on the external drive and click OK.
- Choose Photos › Settings, click General, and click Use as System Photo Library.
- Click iCloud, select iCloud Photos, and choose Download Originals to this Mac.
- Leave the Mac on, connected and awake while everything downloads.
- When it's done and you've checked it, remove the old library from Pictures.
The catch: anything that lives only in the old library stays there. That includes uploads that never finished and referenced files. Keep the old library until you're sure the new one has everything.
Which route suits you?
| Your situation | Better route | Why |
|---|---|---|
| No iCloud Photos | Move the library | It's the only copy, so moving keeps everything |
| iCloud Photos with Download Originals | Move the library | No download needed; the copy is already full size |
| iCloud Photos, optimized, fast internet | Either; a new library is simpler | iCloud supplies the originals |
| iCloud Photos, optimized, slow internet | Move the library | Downloading every original could take days |
| Uploads still pending | Move the library | Pending items exist only in the current library |
Living with a library on an external drive
Once the move is done, Photos works the same as before. The difference is that it now depends on a drive that can be missing, asleep or full.
What happens if the drive isn't connected?
Apple is direct about this. If Photos can't find the drive when it opens, it stops using the library stored there and creates a new, empty library in your Pictures folder. Your photos are still safe on the drive; Photos just isn't looking at them.
To get back: quit Photos, connect and turn on the drive, then hold Option as you open Photos and choose your library on the drive. Check in Photos › Settings › General that it's the System Photo Library, and make it so if it isn't.
What about the empty library Photos made?
It's left behind in Pictures. Once your real library is open and working, look at the new one's size with Get Info. If it's tiny and you never added anything to it, you can drag it to the Trash.
If you did import photos into it before noticing, don't delete it. Open your real library and choose File › Import, select the stray library, and import the photos you want to keep.
Can the drive go to sleep?
A spinning hard drive can, and waking it takes a moment. On a Mac laptop, choose Apple menu › System Settings, click Battery, then click Options. Turning off Put hard disks to sleep when possible keeps a hard drive spinning, at the cost of some power.
Apple's macOS 27 list of Energy settings for desktop Macs doesn't include this option.
That matters most during a long iCloud download, when a drive that drops off can interrupt the sync. An SSD doesn't spin down, so it doesn't have this problem.
Do other apps still see your photos?
Apps that let you choose photos with the system's photo picker show the System Photo Library. Apple's instructions say to designate the moved library as the System Photo Library for this reason too, even if you don't use iCloud Photos.
Eject the drive before you unplug it
Quit Photos first, so nothing is writing to the library. Then Control-click the drive in the Finder sidebar and choose Eject, and wait for it to disappear before you pull the cable.
Unplugging a drive while it's in use can damage the files being written, and a library is being written to whenever Photos is open. If macOS warns that a disk wasn't ejected properly, open the library and check it, and run Repair Library if anything looks wrong.
Can the library live on an encrypted drive?
Yes. APFS (Encrypted) is one of the formats Disk Utility offers, and it's a sensible choice for a drive full of personal photos that could be lost or stolen. The drive asks for its password when you connect it, and Photos can open the library once you've unlocked it.
Backing up a library on an external drive
Moving the library changes what your backups contain. A Mac backup that used to include your photos may now leave them out.
Does Time Machine back up the library on the drive?
Only if Time Machine includes that drive. Choose Apple menu › System Settings, click General, click Time Machine, then click Options. If the drive with your library is in the list of excluded items, select it and remove it from the list.
The backup itself must go to a different drive. Apple warns not to keep a Time Machine backup on the drive that holds a library, because their permissions can conflict.
A second copy by hand
Apple's other method is simple: quit Photos and drag the library to another drive. It's a full copy, so it needs as much room as the library, and it's only as current as the last time you made it.
If you keep a copy this way, label it clearly. Two libraries with the same name on two drives are easy to mix up when you later choose one in the Choose Library dialog.
Isn't iCloud Photos a backup?
Not quite. Apple's iCloud Photos article points out that photos aren't duplicated in your iCloud backup, and asks you to keep backup copies of your library. iCloud Photos is sync: a photo you delete on one device is deleted everywhere, after 30 days in Recently Deleted.
A library on an external drive with no backup is a single point of failure. Drives can fail, and a portable drive can be dropped or lost.
Fixing problems after the move
Most problems after a library move come from three things: the drive's permissions, a drive that wasn't connected, or a library Photos needs to rebuild.
| What you see | Likely cause | What to do |
|---|---|---|
| An error while dragging the library | The drive enforces ownership | Turn on Ignore ownership on this volume |
| No Ignore ownership checkbox | The drive isn't formatted for Mac, or was a Time Machine drive | Erase it as APFS, then copy again |
| Photos opens an empty library | The drive wasn't connected when Photos opened | Quit, connect the drive, Option-open Photos |
| iCloud Photos is off after the move | Designating a library turns it off | Turn it on in the iCloud pane |
| Photos behaves oddly or items look wrong | The library needs rebuilding | Back up, then use Repair Library |
How do you fix a permissions error when moving the library?
Select the external drive in Finder and choose File › Get Info. Under Sharing & Permissions, click the arrow if the section is closed, then click the lock and enter your password. Select Ignore ownership on this volume, then drag the library again.
Apple says the checkbox is missing, or can't be selected, if the drive isn't formatted for Mac or was used for Time Machine without being erased. Erase the drive as APFS in that case.
How do you repair the library on the drive?
Back up the library first. Then quit Photos, hold Option and Command, and click Photos in the Dock or in Applications. In the Repair Library window, click Repair. Apple suggests restoring from a Time Machine backup if problems persist.
What if the library on the drive is damaged?
That's what the original and the backup are for. If you haven't deleted the original yet, open it again with the Option key and try the copy later. If you have, restore the library from Time Machine: Apple's steps are to quit Photos, enter Time Machine, select the library in the backup, and click Restore.
If you use iCloud Photos, Apple notes that restoring the System Photo Library brings back photos you deleted since that backup, and uploads them to iCloud again.
Moving the library again
A library on an external drive isn't stuck there. The same steps move it anywhere else.
Back to your Mac
Make sure the Mac's startup disk has room for the whole library first. Then quit Photos, drag the library from the drive to your Pictures folder, open it there, and designate it as the System Photo Library if you use iCloud Photos. Delete the drive's copy only once the one on the Mac works.
To a bigger drive
Quit Photos and drag the library from the old drive to the new one. Format the new drive as APFS first, and check the Ignore ownership on this volume box if Finder reports a permissions error. Then open it, designate it, and keep the old drive's copy until you've checked the new one.
To a new Mac
Connect the drive to the new Mac, hold Option as you open Photos, and choose the library on the drive. Designate it as the System Photo Library and turn on iCloud Photos there if you use it.
Use the library on one Mac at a time, and quit Photos before you eject the drive.
Mistakes to avoid
The library looks like a single item, so it's tempting to treat it like any other file. These are the ways a move goes wrong.
| Don't | Why | Instead |
|---|---|---|
| Delete the original before checking the copy | A bad copy or a failing drive leaves no good library | Use the copy for a day or two first |
| Copy files out of the library in Finder | Apple warns this can delete or corrupt the library | Move the whole library, or export from Photos |
| Use your Time Machine drive | Apple says it can't hold a library | Keep the library and its backup on separate drives |
| Open Photos before connecting the drive | Photos makes an empty library and stops using yours | Connect the drive first, every time |
| Choose the wrong library as System Photo Library | Its photos merge into iCloud and can't be unmerged | Check the name and location first |
| Forget referenced files | They stay on the Mac and aren't backed up | Consolidate them before the move |
Should you move the library or just optimize it?
If you use iCloud Photos and simply want space back on the Mac, Optimize Mac Storage is less work: no drive to carry, no backup to rearrange. The post on Photos taking up space on a Mac explains how it works and why it doesn't shrink the library right away.
An external drive is the better answer when your library is larger than your iCloud plan, when you don't use iCloud Photos, or when you want every original kept on hardware you own.
What else can go to the same drive?
A drive bought for photos often has room to spare. Large, rarely opened files are good company: finished video projects, old installers, archives. Copies of old iPhone backups can go there too, as the post on where iPhone backups are stored explains.
Local AI models move the same way, through each app's own folder setting, as the post on keeping AI models on an external drive explains. The guide to freeing up space on a Mac covers what else is worth moving or removing.
How the app does it
Wombit is a native Mac app that shows what's using your storage and explains every item in plain language. It scans the whole disk or any folder, reading only names, sizes and dates, and file names and paths never leave your Mac.
Every Photos library in your home folder appears on the map with its real size, explained from the catalog's Photos library entry, including old libraries you may have forgotten. After a move, a fresh scan shows the space the library used as free, and any empty library Photos made in Pictures shows up too.
~/
**/ *.photoslibrary A Photos library: your photos and videos, your edits and albums, and the previews Photos makes from them.
Managed by macOS · Explained only: the app shows you how
The library is Managed by macOS: the app never moves it, deletes it or changes anything inside it. It explains how to make it smaller with Photos' own settings, or move it to an external drive with Apple's steps, as above. Nothing about your photos leaves your Mac.
The scan, the map and the explanations are free. Cleanup for the items the app can act on is PRO: one payment of $4.99 with lifetime access. Every Pro tool's review is free to open, so you see what would go and why before you buy.
Frequently asked questions
Can I use iCloud Photos with a library on an external drive?
Yes. Open the library on the drive, choose Photos › Settings, click General and click Use as System Photo Library. That turns iCloud Photos off, so turn it on again in the iCloud pane. Keep the drive connected whenever Photos is open.
What format should an external drive be for a Photos library?
APFS or Mac OS Extended (Journaled), Apple says. A drive formatted as exFAT or MS-DOS (FAT) has to be erased first. You can check a drive's format by selecting it in Finder and choosing File › Get Info.
Can I keep my Photos library on my Time Machine drive?
No. Apple says a library can't be stored on a drive used for Time Machine backups, because their permissions can conflict. Keep the library on one drive and back it up to another.
Why did Photos open an empty library after I moved mine?
Photos couldn't find the drive when it opened, so it stopped using your library and made a new, empty one in Pictures. Quit Photos, connect the drive, hold Option as you open Photos and choose your library on the drive.
Do I need to delete the original Photos library after moving it?
Only if you want the space back, and only after the copy on the drive has opened and you've checked it. Then drag the original from Pictures to the Trash and empty the Trash. Until you do, the library takes space in both places.
Will moving my Photos library affect the photos on my iPhone?
No. Moving the library changes only where your Mac keeps its copy. With iCloud Photos, your iPhone keeps syncing with iCloud as before, once the moved library is set as the System Photo Library and iCloud Photos is back on.
Why do I get a permissions error when copying the library to a drive?
The drive is enforcing file ownership. Select it in Finder, choose File › Get Info, unlock Sharing & Permissions and select Ignore ownership on this volume. If the checkbox is missing, the drive isn't formatted for Mac and needs erasing.