Move a 1 TB iCloud Photo Library to an External Drive (Before You Cancel iCloud)
The setup is common enough that it comes up on Apple support forums every week. A photo library that has grown past 1 TB, a MacBook Air with a 256 GB SSD, an iCloud+ bill you would like to stop paying, and an external drive bought for the purpose. Every photo is safely in iCloud. All that is left is to get them onto the drive.
Then the first step everyone tries, turning on “Download Originals to this Mac”, fails in a way that makes the whole plan look impossible.
Why that first step cannot work
Download Originals to this Mac does exactly what it says: it replaces the
space-saving thumbnails in your current library with full size files. The
current library is the one in your Pictures folder, on the startup disk.
Asking a 256 GB disk to hold 1 TB of originals ends with a full disk, a
stalled download, and macOS complaining it is out of space.
Nothing about that failure means the photos cannot be moved. It means the library has to be somewhere else before the originals are requested. The order is the entire trick.
The order that works
- Format the drive as APFS. Disk Utility, erase, APFS. Mac OS Extended (Journaled) is fine on older machines. Not exFAT, not FAT32, not a network share, none of which can hold a Photos library.
- Quit Photos, then copy
Photos Library.photoslibraryfromPicturesto the drive. Copy it, do not move it, until the copy is proven to work. Expect this to take hours at 1 TB, and expect the Mac to need to stay awake for it. - Hold Option while launching Photos. The library chooser appears. Select the library on the external drive.
- Photos > Settings > General > Use as System Photo Library. Only the System Photo Library is allowed to use iCloud Photos, so skipping this leaves the download pointed at the old library.
- Now turn on Photos > Settings > iCloud > Download Originals to this Mac. Full size files start landing in the library on the external drive.
- Let it finish. Keep the drive connected and the Mac awake. This is the long part.
- Make a second copy, then cancel iCloud+.
Steps 4 and 5 are the ones people reverse, and reversing them is what fills the startup disk.
Move the library, do not export the photos
The other common instinct is to select everything in Photos and export it to a folder on the drive. It feels tidier, and it quietly throws away most of what you were trying to keep.
A .photoslibrary bundle is a database plus originals. Inside it:
- Edits are non-destructive. The library holds the untouched original plus a list of adjustments. Export gives you a flattened file and the ability to revert is gone.
- A Live Photo is two files, a still and a short QuickTime movie, tied
together by the database. Exported, they become either a plain still or a
still plus an unrelated-looking
.mov. - RAW and JPEG pairs collapse. A photo shot as RAW+JPEG is one item with two files behind it. Export hands you whichever one the export options picked.
- Albums, faces, keywords, memories, and favorites are database rows. They do not exist in an exported folder at all.
- Capture date and location survive only as EXIF, which some export settings strip, and which nothing restores afterwards.
Moving the bundle keeps every one of those, and you can still export individual photos any time later. Exporting first is the one decision here that cannot be undone.
Verifying before you cancel anything
Two checks, both quick:
- The bottom of the Library view in Photos reports sync status. It should say the library is up to date, with no “Downloading” counter left.
- In Finder, Get Info on the library. Its size should be in the same neighbourhood as your iCloud Photos usage in System Settings. A library still full of thumbnails is smaller by an order of magnitude, and that difference is easy to spot.
Only after both look right should the iCloud+ plan change. When you downgrade, iCloud Photos stops syncing and content over the new limit is removed from iCloud after a grace period. That grace period is not a backup.
One drive is not a backup
When the download finishes and iCloud is cancelled, that external drive holds the only copy of every photo you have. It is a single mechanical or flash device, usually carried around, usually unplugged and replugged daily.
Time Machine onto a second drive, a clone of the first drive, or a cheaper cloud tier used purely as an archive all work. The specific choice matters much less than there being two of something before iCloud stops holding a copy for you.
The format question, later
Moving a library changes no formats. iPhone photos stay HEIC, RAW stays RAW, and on the Mac that is invisible: Preview, Photos, and Quick Look read all of it.
It stops being invisible the first time the drive meets something that is not a Mac. Windows needs codec extensions before File Explorer will even show a HEIC thumbnail, and TVs, digital photo frames, and car head units frequently refuse HEIC outright. The fix at that point is to convert copies, not the library:
- For a handful of photos, select them in Photos and use File > Export > Export Unmodified Original, or export as JPEG directly.
- For a whole folder that has already been copied to a Windows machine, this site’s app, HEIC Batch Converter (disclosure: written by the author of this site), converts folders and subfolders to JPG in one pass and ships its own decoder, so the Windows codec extensions are not needed. It is Windows only. On the Mac side, Photos’ own export or Preview’s batch export does the same job.
Either way, keep the library as the master and treat JPGs as disposable copies for whatever device needed them.
Bottom line
| Question | Answer |
|---|---|
| Turn on Download Originals first? | No. That is the step that fills the startup disk |
| Correct order | Copy library to drive, Option-launch, set as System Photo Library, then Download Originals |
| Drive format | APFS or Mac OS Extended (Journaled). Not exFAT, not a network share |
| Export instead of moving? | No. Exporting drops edits, Live Photo videos, RAW pairs, albums, and sometimes dates |
| When to cancel iCloud+ | After the download completes, is verified, and a second copy exists |
| Photos stay HEIC? | Yes. Convert copies later if a non-Apple device needs JPG |
Frequently asked questions
Why can't I just turn on Download Originals first?
Because Download Originals downloads into whichever library is currently in use, and that is the one on your startup disk. On a 256 GB Mac with a 1 TB library, the disk fills, the download stalls, and macOS starts warning about free space. Moving the library first is what redirects the download onto the external drive.
Can the photo library live on an exFAT drive?
No. Photos requires APFS or Mac OS Extended (Journaled). exFAT and FAT32 do not support the permissions and hard links inside the library bundle, and network volumes are not supported either. Erase the drive as APFS in Disk Utility before you copy anything to it.
Should I export my photos instead of moving the library?
No, exporting is the lossy path. Edits, the video half of every Live Photo, RAW and JPEG pairs, albums, faces, keywords, and often the capture date and location are properties of the library bundle rather than of the exported files. Moving the whole bundle keeps all of it, and you can still export individual photos later.
What happens to Live Photos?
Inside the library each Live Photo is a still image plus a short QuickTime movie, kept together by the library database. Move the bundle and they stay paired. Export them and you get either a still with no motion, or a still and a separate .mov file that nothing outside Photos knows are related.
How do I know the download actually finished?
Photos shows the sync status at the bottom of the Library view, and it should say the library is up to date with no pending downloads. As a second check, the library size in Finder should be roughly your iCloud Photos usage. A library that is still mostly thumbnails will be dramatically smaller than the iCloud figure.
What happens to my photos when I cancel iCloud+?
iCloud Photos stops syncing, and content above your new storage limit is eventually removed from iCloud. Apple gives a grace period, commonly cited as 30 days, but there is no reason to lean on it. Finish the download, verify it, make a second copy, and only then downgrade.
Will my photos still be HEIC after this?
Yes. Moving a library does not change formats, so iPhone photos stay HEIC and RAW files stay RAW. That is fine on a Mac, which reads both. It becomes a problem the day you hand the drive to a Windows PC, a TV, or a photo frame, and the answer then is to convert copies rather than the library.