A shared Mac: which user account is using all the space

9 September 2026 · 6 min read

On a Mac with more than one account, the Storage screen in System Settings itemizes your own files in detail and lumps everyone else’s into a single figure you cannot open. That is a privacy decision rather than an oversight, and it is why a family Mac can be full without anybody being able to say why.

To get per-account numbers you have to measure the home folders directly. It takes one Terminal command, one permission grant, and some patience while it counts.

What Storage settings will and will not tell you

System Settings, General, Storage gives you a bar across the top and a list of categories beneath it: Applications, Documents, Photos, Mail, Messages, System Data, Trash, and, if the Mac has more than one account, a category covering other users.

Two things to understand before you trust that screen. Everything it itemizes in detail belongs to the account you are logged into: Documents means your Documents, Photos means your Photos library. And other people’s data is summed and left closed. You cannot expand it.

So the screen is genuinely useful for your own account and close to useless for the question you are asking. It will tell you that 380 GB belongs to other people; it will not say which people. What System Data is on a Mac covers the other category on that screen that never adds up.

Measure every home folder from Terminal

The command that answers the question is du, which walks a folder and adds up what it finds. You need an administrator account and you need to be prepared to wait: on a full disk this can take ten minutes or more, because it reads directory information for every file on the Mac.

One preparation step first, and skipping it is the usual reason the numbers come back wrong.

Give Terminal Full Disk Access. Since macOS Catalina, folders such as Desktop, Documents and Downloads are protected by the privacy system, and that protection applies even to commands run as an administrator. Without the grant, du reports a stream of Operation not permitted lines and undercounts every account, sometimes by hundreds of gigabytes. Go to System Settings, Privacy and Security, Full Disk Access, and switch on Terminal. Quit and reopen Terminal afterwards, because the change applies only to a newly launched process.

Then run:

sudo du -shx /Users/*

Enter your password when asked. The flags are worth knowing: -s gives one total per folder rather than a line for everything inside it, -h prints human-readable sizes, and -x stops it wandering onto mounted drives and counting your backup disk as part of somebody’s home folder.

For a sorted list rather than a jumble, ask for kilobytes and sort numerically:

sudo du -skx /Users/* | sort -n

The largest account is the last line. Then point the same command at that one account to see where inside it the space has gone:

sudo du -shx /Users/theirname/*

Turn Full Disk Access for Terminal back off when you have finished, if you would rather not leave it granted.

The folders that belong to nobody

Three locations on a shared Mac are not anybody’s home folder, and they are regularly the answer.

/Users/Shared. The drop box every account can write to. Because nothing ever prompts anybody to clean it, it accumulates installers, video files and folders somebody moved there once to pass along. Check it early. It is the one place on a shared Mac where you can usually delete things without asking, though it is still polite to look first.

/Users/Deleted Users. When somebody deletes an account, macOS offers to save that person’s home folder as a disk image rather than removing it. Most people accept, because it sounds like the careful option, and the disk image lands here and is never opened again. If this folder exists on your Mac, what is inside it is a complete copy of a former account, and it is often the single largest recoverable item on the machine.

The Guest account. Its home folder is emptied at logout, so it is never the answer. Worth knowing so you can stop looking at it.

What is usually large inside somebody else’s account

If one account turns out to be dominant, these are the places to look, in the order they are usually worth checking:

1. iPhone and iPad backups, in ~/Library/Application Support/MobileSync/Backup. Several generations of backups for a device the person no longer owns is a common find, and each can be tens of gigabytes. Find and delete old iPhone backups on a Mac covers reading them safely.
2. A Photos library, in ~/Pictures. Each account has its own, so two people with the same 200 GB of family photos means 400 GB on the disk.
3. Downloads, which nobody empties.
4. The Trash, at ~/.Trash. Emptying yours does not touch theirs, only that account can empty it, and files sitting there still occupy the disk.
5. Developer folders, if that person writes code. Xcode data and package caches get large and are almost entirely regenerable.
6. Mail, in ~/Library/Mail, on an account that kept every attachment since 2014.

What to do once you know

The answer here is usually social rather than technical. Somebody has to be told, and it should be with a number and a specific folder rather than a general complaint about the Mac being full.

Do not delete files from another person’s home folder. Even with an administrator password, even when you are certain. You cannot see what they are working on, macOS gives you no undo, and one deleted project ends the arrangement of sharing a Mac. Send them the path and let them look.

Point them at their own Storage screen. Once they log in, System Settings, General, Storage itemizes their account properly, the same way it does yours. That is the one place where the built-in tool does exactly what is needed.

Consider whether an account is still in use. An account nobody has logged into for two years is a different question from an active one. Delete it in System Settings, Users and Groups: select the account and choose to delete it. macOS offers to keep the home folder as a disk image, to leave it in place, or to delete it. Once you have confirmed nothing in there is needed, deleting the home folder is the option that recovers the space. The disk image option is what creates /Users/Deleted Users in the first place.

Move shared media off the internal disk. Family photos and video that three accounts each keep a copy of are better on one external drive everybody can reach.

If you would rather see this as a list than assemble it from Terminal, Crumb audits the whole Mac rather than just the account you are logged into, and includes a cross-user view showing which account is using the space. The whole-Mac audit is read-only and free; the cross-user breakdown is part of the paid unlock. It will not delete anything without a plan you have approved, which is the right default on a shared machine.

Questions

Can I see another account’s files without their password? As an administrator you can read most of them, though the privacy-protected folders need Full Disk Access as described above. Being able to is not the same as it being reasonable. Measuring sizes is fair on a machine you administer; browsing somebody’s documents is not.

Why does du report a smaller total than Storage settings? Several reasons stack up. Local Time Machine snapshots hold on to deleted data and are not inside anybody’s home folder. Purgeable space is counted differently depending on who is asking. And if Full Disk Access is not granted, du is simply not seeing everything. Expect the two numbers to be close rather than identical.

Is one account per person still worth it? Yes, for anything beyond occasional use. Separate accounts keep browser sessions, documents and app settings apart, and they make exactly this question answerable. The cost is duplicated media, which is better solved with an external drive than by going back to a single shared login.