To use an external hard drive to free up space on a Mac, move the large things whose apps are built to live on another drive. Each has a supported way to move, and it's worth using.
The good candidates are the Photos library, Music and Apple TV media, iMovie and Final Cut Pro libraries, Logic Pro's sound library, game libraries, virtual machines, local AI models, and finished projects and archives.
Leave the rest where macOS put it. Apps, your home folder and its Library, iCloud Drive and the caches apps use every day are expected on the startup disk, and moving them by hand breaks things in ways that are hard to trace.
Format the drive as APFS, eject it before you unplug it, and remember one rule: a drive that holds the only copy of something isn't a backup. Time Machine needs a disk of its own, and your new drive needs backing up too.
The rest of this post covers choosing the drive, moving each kind of item the way its owner supports, what to leave alone, and living with a Mac whose biggest libraries are on a drive that can be unplugged.
What moves well to an external drive
The best candidates are large, self-contained and owned by one app that knows how to find them somewhere else. Here's the whole list, with the way each one moves.
| Item | How it moves | Drive format | If the drive isn't connected |
|---|---|---|---|
| Photos library | Quit Photos, drag the library, open it there | APFS or Mac OS Extended (Journaled) | Photos makes a new, empty library |
| Music and Apple TV media | Each app's Files settings | APFS | Items on it can't play |
| iMovie library | Quit iMovie, drag the library | APFS or Mac OS Extended (Journaled) | iMovie opens a new, empty library |
| Final Cut Pro library | Copy to Library or drag it | APFS | It can't open until you connect it |
| Logic Pro sound library | Drag the bundle, or Relocate Sound Library | APFS or Mac OS Extended (Journaled) | Logic Pro asks you to Retry, Ignore or Reset |
| Steam games | Settings › Storage, then Move | APFS | Those games can't start |
| Virtual machines | Each app's move or folder setting | APFS | The machine can't start |
| Finished projects, archives | Copy, check, then remove the original | Any Mac format | Nothing breaks; the files wait |
The formats come from Apple's support articles for its own apps. For the others, APFS is the safe choice on a drive used only with Macs.
Why use each app's own way to move?
Because the app needs to know where its library is. Photos, iMovie, Final Cut Pro and Logic Pro can each use a library from wherever you put it, once you open or relocate it with the app. Drag a folder out of your Library behind an app's back, and it finds nothing and starts again.
The app's own way also tells you what it needs: which format, which drive types to avoid, and what happens when the drive is missing. That's information you'd otherwise learn the hard way.
What's worth moving first?
The largest item you open least. For most people that's the Photos library, followed by finished video projects, game installs and old phone backups. On a developer's Mac, virtual machines and local AI models often come first.
Look at the sizes before you buy anything. System Settings › General › Storage shows the categories, and Finder's File › Get Info on a library shows its size. If a single library makes up most of what you'd move, size the drive for that library and its growth.
Choosing the drive
Three things decide how well an external drive works for this: whether it's an SSD or a hard disk, which port and cable connect it, and how much room it leaves you to grow.
SSD or hard disk?
An SSD for anything you'll open often, such as a Photos library, a game library or a virtual machine. Apple's Disk Utility guide says APFS is optimized for flash and SSD storage, though it also works on traditional hard disks.
A hard disk holds more for the money and suits archives you open now and then: finished projects, old backups, a second copy of a library. Parallels, for one, recommends an SSD if you'll run a virtual machine straight from an external drive, and Steam recommends against installing Steam itself on an external hard drive.
Which port and cable?
Use the fastest port your Mac has, and a cable rated for that speed. Apple's tech specs list these maximum speeds for current Macs:
| Port | Up to | Suits |
|---|---|---|
| Thunderbolt 5 | 120 Gb/s | The fastest external SSDs, video work, virtual machines |
| Thunderbolt 4 or USB 4 | 40 Gb/s | Fast SSDs, photo libraries, games |
| USB 3 | 10 Gb/s | Most SSDs and hard disks, archives |
| USB 2 | 480 Mb/s | Small files only; large libraries crawl |
The MacBook Neo has two ports that look alike: one USB 3 and one USB 2. Plug the drive into the USB 3 one. On the Mac mini, the rear Thunderbolt ports are far faster than the front USB-C ports.
How big a drive?
Big enough for what you're moving now, plus its growth. A Photos library only gets bigger, and with iCloud Photos and Download Originals to this Mac, it grows to the size of your whole iCloud collection.
A drive at least twice the size of what you're moving is a comfortable start. Running an external drive nearly full brings back the same problem you bought it to solve.
Should you encrypt the drive?
If it will leave the house, yes. A drive full of photos and projects is easy to lose. Disk Utility can format a drive as APFS (Encrypted), and Apple says you then enter the password whenever you connect it.
Encrypting this way erases the drive, so do it before you copy anything. Apple's Disk Utility guide adds that you can change the password later with File › Change Password.
Name the drive once, and keep the name
Some apps remember a library by its path, and the path includes the drive's name. Apple warns that Logic Pro 11 and earlier can't find a relocated sound library if you rename the drive. Pick a plain, lasting name when you erase it, such as Media or Archive.
Can a USB flash drive or SD card do the job?
Not for libraries. Apple warns against keeping a Photos library on an SD card or USB flash drive, to avoid possible data loss, and says it doesn't recommend them for iMovie libraries either. They're fine for carrying files around, not for a library that's written to every time you open it.
Logic Pro's sound library is an exception: Apple's article says it can live on an SSD or a USB thumb drive.
Formatting the drive
Many drives come formatted for Windows, as exFAT or FAT. That's fine for swapping files with a PC, but Apple's apps want a Mac format for their libraries, and the App Store's large-app setting needs APFS.
Which format should you choose?
APFS, for a drive used only with Macs. Apple's articles for Photos and iMovie accept APFS or Mac OS Extended (Journaled), Final Cut Pro asks for APFS, and the App Store installs large apps only on APFS drives.
If the drive will travel, consider APFS (Encrypted): it asks for a password when you connect it, so a lost drive doesn't expose your photos. The post on APFS, Mac OS Extended and exFAT compares the formats in detail, including when exFAT is still the right choice.
How do you check and change the format?
Select the drive in Finder and choose File › Get Info: the format is listed under General Information. Apple's Final Cut Pro article gives the same check.
To change it, copy anything you need off the drive first, because erasing deletes everything on it. Then Control-click the drive in the Finder sidebar, choose Erase Disk, pick a format and click Erase. Disk Utility's Erase button does the same, with more options.
Can one drive hold Time Machine backups and your files?
Not for your libraries. Apple says a Photos, iMovie or Final Cut Pro library can't be stored on a storage device used for Time Machine backups. Use a separate drive for each.
For other files, Apple says you can add a second APFS volume to a Time Machine disk; the volumes then share the drive's space. Remember that one drive failing then takes both the backup and the files with it.
Moving Apple's libraries
Apple documents the move for each of its media apps. The steps differ a little, but the pattern is the same: quit the app, copy the library, open it from the drive, check it, and only then remove the original.
Photos
Quit Photos, drag Photos Library from your Pictures folder to the drive, and double-click it there to open it. If you use iCloud Photos, choose Photos › Settings › General and click Use as System Photo Library, then turn iCloud Photos back on.
Apple warns that if the drive isn't connected when Photos opens, Photos stops using the library and makes a new, empty one in Pictures. The post on moving the Photos library to an external drive covers the checks, the iCloud choices and the errors people meet.
Music
In Music, choose Music › Settings, click Files, then click Change to choose a folder on the drive for files you import from now on. Apple notes that songs already imported stay where they are, and that you shouldn't move the Music folder itself.
Apple also describes keeping a separate music library on an external drive: hold Option as you open Music and click Create Library or Choose Library. That suits a large collection of imported music you don't need every day.
The Apple TV app
The TV app has the same kind of setting. Choose TV › Settings, click Files, and under Media folder location, click Change to pick a folder on the drive for the movies and shows you import.
Purchases from Apple can usually be downloaded again, so moving them gains little. Home videos you added yourself may exist only in that folder, so treat them like photos.
iMovie
Quit iMovie, open your Movies folder, and drag iMovie Library to the drive. When the copy finishes, double-click the library there to open it, and click OK if iMovie asks for access to a removable volume.
Apple says to make sure the moved library has all your media before you drag the original to the Trash and empty it. If the drive isn't connected next time, iMovie opens a new, empty library in Movies; connect the drive and open the moved one again.
Final Cut Pro
Final Cut Pro can copy a library to a drive for you with File › Copy to Library › New Library, including media stored outside the library. Apple's other route is to quit Final Cut Pro and drag the library file in Finder.
Before moving, File › Delete Generated Library Files removes render, optimized and proxy files that Final Cut Pro can make again, which can shrink the library a lot. Apple asks for an APFS drive.
Logic Pro's sound library
Logic Pro 12 keeps its sounds in one bundle, Logic Pro Library.bundle, in your Music folder. Apple says you can drag it to another drive at any time and delete the original once it's copied.
Older versions use Logic Pro › Sound Library › Relocate Sound Library. For those, Apple warns not to rename the drive afterwards, and says to allow Logic Pro access to removable volumes in Privacy & Security if it can't relocate the library.
Games, virtual machines and AI models
These are often the largest single items on a Mac, and each tool has its own way to put them on another drive.
Steam and other games
Steam lets you add a library folder on any drive: open Steam's Settings, click Storage, and add a new location with the + button. To move installed games, select the drive they're on, select the games and click Move. No downloading again.
For games from the App Store, App Store › Settings › Download and install large apps to a separate disk puts apps larger than 1 GB on an external APFS drive of your choice.
Parallels Desktop
Parallels lets you choose where new virtual machines go: open Parallels Desktop's Preferences, click General, and choose a folder from Virtual Machines Folder. Existing machines stay where they are.
To move one, shut it down, find its .pvm file (or .macvm for macOS machines on Apple silicon) in the Parallels folder, and copy it to the drive. Parallels' guide says you can then run it from the drive by double-clicking it.
UTM and other virtual machine apps
UTM has a Move action for this. Its documentation describes it as moving a virtual machine to another path, an external hard drive for example. Remember that removing a machine from UTM's list deletes its data only when it's still in UTM's default folder.
The post on virtual machines and the space they take covers VMware Fusion, VirtualBox and the others.
Local AI models
Ollama's app has a Model location setting, and LM Studio lets you change its models folder. The trick is to copy the existing models to the drive first, then point the app at them, so nothing downloads again.
The post on keeping AI models on an external drive goes through each tool's setting and what happens when the drive is missing.
iPhone backups, projects and caches
Some large items don't belong to one library app. They move fine, as long as you're clear about which copy is which.
iPhone and iPad backups
Finder has no setting to back up a device straight to an external drive. What you can do is copy a backup there as an archive, check it, and delete it from the Mac; to restore from it, copy it back first.
The post on where iPhone backups are stored shows how to find each backup with Manage Backups and Show in Finder, and why linking the backup folder to a drive is a bad idea.
Finished projects and archives
Video projects you've delivered, old photo exports, installers you might need again and zip archives are the simplest things to move. They're plain files: drag them to the drive, and Finder copies them because it's another disk.
Then check the copy. Open a few files from the drive and compare sizes with File › Get Info. Only then move the originals to the Trash. Finder's Move to Trash can be undone with Put Back until you empty the Trash.
What about large files you haven't opened in years?
Treat them as possibly the only copy. A video of an event or a project archive from years ago may exist nowhere else. Copy it to the drive and to a second place before removing it from the Mac.
Why keep the originals for a few days?
Because a copy can look complete and still be missing something, and a new drive can fail early. Using the moved library for a couple of days, before you delete the original, is the cheapest insurance you'll get.
Apple's steps for iMovie and Final Cut Pro both say to check that the moved library has all your media before you delete the original.
Video and media caches
Caches usually stay put, but some apps let you choose where they go. Premiere Pro and the other Adobe video apps have a media cache location you can point at a fast external drive, as the post on Adobe's media cache explains.
Spotify's desktop app can move its cache too: its support page says to click Change location in its storage settings. Downloads are different; Spotify's advice for those is to remove downloaded tracks you don't need.
What not to move to an external drive
Some things are large but belong on the startup disk. Moving them by hand saves space for a day and costs hours later.
| Item | Why it stays | What to do instead |
|---|---|---|
| Apps in Applications | Many expect to be there and update in place | Uninstall apps you don't use |
| Your home folder | macOS and every app expect it on the startup disk | Move big items out of it, one by one |
| The Library folder | Apps keep their settings and data there | Use each app's own setting to move its data |
| iCloud Drive | macOS has no setting to put it on another disk | Turn on Optimize Mac Storage |
| Caches apps use every day | Apps recreate them in the old place anyway | Use an app's own cache location setting, if it has one |
| Streaming downloads | They're tied to the app that downloaded them | Remove downloads you've watched or heard |
Why not move apps?
Most apps are installed in Applications and update there. The App Store's large-app setting is the supported exception, for apps larger than 1 GB on an APFS drive. Otherwise, uninstalling apps you don't use frees more space with no drive to keep connected.
Why not move the home folder?
Your home folder holds your Library, your settings and the data of nearly every app. If it lived on a drive that wasn't connected, apps would have nowhere to find their data. Moving the large things inside it, one at a time, gets the same space back safely.
Can you move iCloud Drive or another cloud folder?
Not iCloud Drive: there's no setting for its location, and its folder in your Library is one to leave alone. Use Optimize Mac Storage or Remove Download instead, which keep files in iCloud and free the space on the Mac.
Other cloud services set their own rules, and only some allow their folder on an external drive. The post on cloud drive storage on a Mac covers Dropbox, Google Drive, OneDrive and Box one by one.
What about downloads from streaming apps?
Offline downloads from video and music services belong to the app that made them and play only inside it. The post on the space streaming apps take explains where they're kept and how to remove what you've finished with.
Ejecting safely and living with the drive
Once your libraries are on a drive, the drive becomes part of your Mac's routine. A few habits keep it healthy.
How do you eject the drive?
Quit the apps that use it first, such as Photos or a game. Then select the drive and choose File › Eject, or click the eject button next to its name in the Finder sidebar. Wait until it disappears before you pull the cable.
An exFAT drive needs this most. Seagate's instructions point out that exFAT isn't a journaled file system, so it must be ejected safely to prevent corruption.
What if the Mac won't eject it?
Apple says a disk may not eject if an app is using it. Quit the apps that might be, or close the documents open from the drive, then try again. Pressing Command-Tab shows which apps are open.
What happens when the drive isn't connected?
It depends on the app. Photos and iMovie open a new, empty library on your Mac; connect the drive and open the moved one again. Logic Pro offers Retry, Ignore or Reset. Games and virtual machines on the drive simply can't start.
Plug the drive in before you open the apps that use it. On a desktop Mac, leaving the drive connected all the time avoids the question.
Why does the drive look full with nothing on it?
Usually because of what Finder doesn't show: files in the drive's own Trash, Time Machine snapshots, another volume sharing the space, or hidden folders. The post on an external drive that's full with no files goes through each cause.
What if Finder says you don't have permission?
Select the drive, choose File › Get Info, unlock Sharing & Permissions, and select Ignore ownership on this volume. Apple's Photos article describes this fix, and notes that the checkbox is missing on drives that aren't formatted for Mac.
A drive with the only copy isn't a backup
Moving a library to an external drive changes where your only copy lives. Before, your Mac's disk held it; now a drive you carry, knock and unplug does.
Time Machine needs its own disk
Apple says the entire APFS volume used for Time Machine is reserved for backups, and that Photos, iMovie and Final Cut Pro libraries can't be stored on a Time Machine drive. So plan for two drives: one for your libraries, one for backups.
Include the drive in Time Machine
Open System Settings › General › Time Machine and click Options. If your new drive appears in Exclude from Backups, select it and click the remove button, so Time Machine backs it up along with your Mac.
Or keep a second copy
If you don't use Time Machine, copy the libraries to a second drive now and then. It's only as current as the last copy, but it turns one point of failure into two. iCloud Photos also keeps your photos in iCloud, though it's sync, not a backup: deletions sync too.
How to use an external hard drive to free up space on a Mac, step by step
Here's the whole process in order, from a full Mac to space back and a backup in place.
- Find the largest items in System Settings › General › Storage and with File › Get Info on libraries.
- Buy a drive at least twice the size of what you'll move, an SSD for anything you open often.
- Copy anything already on the drive elsewhere, then erase it as APFS.
- Move each library with its app's own steps, starting with the largest.
- Open each moved library from the drive and check it: oldest and newest items, a few large files.
- Use the Mac for a few days, then move the originals to the Trash and empty it.
- Add the drive to Time Machine, or set up a second copy.
- Make a habit of connecting the drive before opening the apps that use it.
How much will you get back?
Exactly the size of the originals you remove, once the Trash is empty. Storage settings can take a few minutes to update after a large deletion.
What if moving isn't enough?
If the space is going to apps and their data, which belong on the internal disk, an external drive won't fix it. The post on whether you can upgrade a Mac's storage covers what's possible, what Apple charges and when a new Mac makes sense.
Mistakes to avoid
Most problems with libraries on external drives come from a handful of shortcuts. These are the ones that cost people their data or their afternoon.
| Don't | Why | Instead |
|---|---|---|
| Delete the original before checking the copy | A bad copy leaves no good library | Use the moved library for a few days first |
| Keep a library on an SD card or flash drive | Apple warns of possible data loss | Use an SSD or hard disk |
| Put libraries on your Time Machine drive | Apple says they can't be stored there | Use one drive for each |
| Unplug the drive without ejecting it | Files being written can be damaged | Quit the apps, then eject |
| Rename the drive after moving things to it | Some apps lose track of their libraries | Choose a lasting name when you erase it |
| Treat the drive as your backup | It now holds the only copy | Back it up to another drive |
Will moving libraries make the Mac faster?
No. Moving files frees space on the startup disk; it doesn't make the Mac faster. What it does is give macOS room to install updates and give apps room to work, which matters when a disk is nearly full.
How the app does it
Wombit shows what's using your storage and explains each item, so you can see which libraries are worth moving before you buy a drive. It scans the whole disk or any folder, reading only names, sizes and dates, and file names and paths never leave your Mac.
The libraries in this post appear on the map with their real sizes, explained from the catalog with the owner's way to make them smaller or move them. After a move, a fresh scan of the startup disk shows the space as free, and any empty library Photos or iMovie made shows up too.
The Photos library is Managed by macOS: the app never moves it, deletes it or changes anything inside it. Logic Pro's sound library is Usually safe. Music and TV media, iPhone backups, iMovie and Final Cut Pro libraries, games, virtual machines, AI models and large old files are Review first, because they may be the only copy: nothing starts checked.
~/
**/ *.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
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Music/ Music/ {Media,Media.localized} Songs, music videos and other files in your Music library, including music you imported and songs you downloaded.
Review first · Explained only: the app shows you how
~/
Library/ Application Support/ MobileSync/ Backup/ * Backups of an iPhone, iPad or iPod touch that were made on this Mac, one folder for each device.
Review first · Moves it to the Trash
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**/ *.imovielibrary An iMovie library: the video and photos you imported, your projects, and render files iMovie creates.
Review first · Explained only: the app shows you how
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**/ *.fcpbundle A Final Cut Pro library: your events and projects, media copied into it, and render, optimized and proxy files.
Review first · Explained only: the app shows you how
~/
Music/ Logic Pro Library.bundle The sound library of Logic Pro 12 and MainStage 4: patches, samples, Apple Loops and the sound packs you download.
Usually safe · Explained only: the app shows you how
~/
Library/ Application Support/ Steam/ {steamapps,SteamApps} Games you installed with Steam, their downloads, and any saves they keep in the game folder.
Review first · Explained only: the app shows you how
~/
Parallels/ *.{pvm,macvm} Parallels Desktop virtual machines
Virtual machines you created in Parallels Desktop, each stored as one package with its disks and settings.
Review first · Explained only: the app shows you how
~/
.ollama/ models Language models you've pulled or created with Ollama, stored as shared layers.
Review first · Explained only: never removed
~/
**/ * Large files not changed in a year
Files of 500 MB or more in your home folder that haven't changed for a year, such as old videos, disk images and archives.
Review first · Moves it to the Trash
The app doesn't move anything to another drive itself; moving stays with each app's own steps, as above. The scan, the map and the explanations are free. Cleanup and the Apple Data actions for iPhone backups and large old files are PRO: one payment of $4.99 with lifetime access. Every Pro tool's review is free to open.
Frequently asked questions
What can I move to an external drive to free up space on my Mac?
Large libraries whose apps support another drive: the Photos library, Music and Apple TV media, iMovie and Final Cut Pro libraries, Logic Pro's sound library, Steam games, virtual machines and local AI models. Finished projects and archives move easily too. Leave apps, your home folder, the Library folder and iCloud Drive where they are.
Can I move applications to an external drive on a Mac?
Mostly no. Apps expect to live in Applications and update there. The exception is the App Store's setting Download and install large apps to a separate disk, which puts apps larger than 1 GB on an external drive formatted as APFS.
What format should an external drive be for a Mac?
APFS, for a drive used only with Macs. Apple's Photos and iMovie articles accept APFS or Mac OS Extended (Journaled), Final Cut Pro asks for APFS, and the App Store installs large apps only on APFS. Use exFAT only if the drive must also work with Windows.
Is an external drive a backup?
Not if it holds the only copy. Once you move a library to a drive and delete the original, that drive is a single point of failure. Back it up with Time Machine to a separate drive, or keep a second copy elsewhere.
Can I use my Time Machine drive to store my Photos library?
No. Apple says a Photos, iMovie or Final Cut Pro library can't be stored on a storage device used for Time Machine backups. Keep the library on one drive and the backups on another.
What happens if the external drive isn't connected when I open Photos?
Photos stops using the library on the drive and creates a new, empty library in your Pictures folder. Your photos are safe on the drive. Quit Photos, connect the drive, then hold Option as you open Photos and choose your library.
Should I use an SSD or a hard disk as an external drive for my Mac?
An SSD for anything you open often, such as a photo library, games or virtual machines. A hard disk costs less per terabyte and suits archives you rarely open. Either way, connect it to the fastest port your Mac has.