How to check storage on a Mac, and what each number means

The fastest way to check storage on a Mac is System Settings › General › Storage. The bar at the top shows how much of your disk is used and how much is available, split into categories such as Applications, Documents and System Data.

For a single number, Finder is quicker: select your disk and choose File › Get Info. For the most precise figures, open Disk Utility and click Info, which lists free space and purgeable space separately.

All three are right, and they rarely agree. They count different things, and the gap between them is often tens of gigabytes. This post goes through every place macOS shows storage, what each figure means, and which one to trust for what you're about to do.

If you only want the short version of why the numbers disagree, the guide to why your Mac's storage numbers don't match covers it on one page. Here we go deeper: every screen, every term, and a worked example from a real Mac.

Check storage on a Mac in Storage settings

Storage settings is the fullest view macOS gives you. It shows the total, sorts what's used into categories, and lets you open most of them to see the largest items.

How do you open Storage settings?

1. Choose Apple menu › System Settings.
2. Click General in the sidebar. You may need to scroll down to see it.
3. Click Storage.

The steps are the same in macOS 27 Golden Gate and macOS 26 Tahoe, and Apple's instructions for the two are word for word the same. They've been the same since macOS Ventura, when System Preferences became System Settings.

Before Ventura, storage lived in Apple menu › About This Mac, under a Storage tab, with a Manage button for the detailed view. If you help someone with an older Mac, that's where to look.

Why does it say Calculating for so long?

Storage settings works its figures out in the background each time you open it. On a full disk, or right after a large change, the categories can show Calculating… for a minute or more, and their sizes can shift while you watch.

Give it time before you read the numbers. If you close the window and open it again a minute later, the totals are usually steadier.

What does the bar at the top show?

The bar comes with a line such as "320 GB of 494 GB used". Each color is a category. Move the pointer over a color to see how much space that category uses.

Apple's guide calls the light gray part at the end free storage space. The figures next to the bar are what's used and what's available, and available can include purgeable space macOS hasn't freed yet. More on that difference below.

What does All Volumes show?

Click All Volumes… for a bar per volume and container on your internal disk. It's useful when your Mac has more than one volume, for example a second macOS install or a volume you made for projects.

APFS volumes in one container share the container's free space. Apple's guide describes a crosshatched area for the space the whole container uses, other volumes included, which is why one volume's free space goes down when another fills up.

What do the categories include?

Below the bar is a list of categories. Most have an information button that opens a list of what's in that category. Apple documents what each one counts, and a few of the definitions are narrower or wider than their names suggest.

Category	What its number counts	Worth knowing
Applications	Apps you installed, not the ones that come with macOS	On a partitioned disk, only apps on the startup partition
Documents	Files in your home folder that fit no other category	Includes photos and videos outside your Photos library
iCloud Drive	Files from iCloud Drive kept on this Mac	Can include Desktop and Documents if they sync to iCloud
iOS Files	iPhone and iPad backups, and their software update files	One backup can take tens of gigabytes
Trash	Items waiting to be erased	Leaves out items deleted from iCloud Drive, and other partitions' Trash
Other Users & Shared	Files of other accounts on this Mac	Size only; you can't open it
macOS	macOS's own apps and files	Size only; macOS manages it
System Data	Everything else: caches, logs, virtual memory, app support files	Size only; changes with the state of your Mac

Media categories such as Music, TV, Books and Podcasts appear when you have purchases or downloads in them. Music Creation counts GarageBand, Logic and MainStage content, and Mail and Messages count your mail and conversations with their attachments.

How do you see how much space each app takes?

Click the information button next to Applications. Storage settings lists your apps with each one's size and when you last used it, and you can sort by either. It counts only the app itself, not the data it keeps in your Library folder, which can be far larger.

For one app, select it in the Applications folder in Finder and choose File › Get Info. The same limit applies: Get Info measures the app, not its caches, settings or documents.

Why can't you open System Data?

Apple describes System Data as files that don't fall into any other category, and says its contents are managed by macOS. Storage settings shows its size and nothing else. To see inside it, you need Finder, the apps that made the files, or a tool that names what's in it.

Older versions of macOS called the same category Other. The System Data guide goes through what's usually in it and what you can do about each part.

Is Delete in Storage settings the same as the Trash?

No, and it's the most important thing to know before you click it. When you select an item in a category and click Delete, macOS asks to confirm and says the item will be deleted immediately and that you can't undo it. It doesn't go to the Trash.

If you might want something back, click Show in Finder instead, and move the item to the Trash there. You keep the chance to put it back until you empty the Trash.

About This Mac and the About pane

People still look for storage in About This Mac, because that's where it lived for years. On current versions it shows basic information about your Mac, and storage has moved to General settings.

Where is storage in About settings?

Choose Apple menu › System Settings, click General, then click About. Near the bottom, a Storage section shows your startup disk with a line such as "174 GB available of 494 GB".

That's the quickest single figure in System Settings. The Storage Settings… button next to it opens the full Storage view described above.

What about System Information?

System Information is the detailed report behind About. Hold down the Option key, then choose Apple menu › System Information. In the sidebar, under Hardware, click Storage.

Each volume gets an entry with its Free space, Capacity, mount point, file system and the physical drive it's on, including its S.M.A.R.T. status. Volumes in the same container show the same free space, because they share it.

It's a plain, precise list, and it's useful when you need the figure for a support request or want to see every volume at once, including external drives.

Check storage in Finder

Finder shows storage in three places: the status bar of any window, the Get Info window of a disk, and the sizes of files and folders. They're the figures you'll see most often.

How do you see free space at a glance?

Open a Finder window and look at the bottom edge. The status bar shows the number of items in the folder and the space available on its disk, such as "24 items, 79.7 GB available". If it isn't there, choose View › Show Status Bar.

The figure is for the disk the folder is on. Open a folder on an external drive and the status bar shows that drive's space instead.

Why does the status bar show iCloud space in iCloud Drive?

In an iCloud Drive folder, the status bar can show the space available in iCloud rather than on your Mac. That's your iCloud plan's free space, a separate pool from your Mac's disk. It's an easy one to misread when you're trying to work out why the Mac is full.

What does Get Info on a disk show?

Select your startup disk, usually Macintosh HD, in the Locations section of the Finder sidebar, then choose File › Get Info or press Command-I. The General section lists:

• Capacity: the size of the disk as macOS formats it.
• Available: what you can use, with the purgeable part in brackets, such as "79.69 GB (5.06 GB purgeable)".
• Used: what's taken.

If your startup disk isn't in the sidebar, choose Finder › Settings, click Sidebar, and select Hard disks under Locations. To keep disks on the desktop as well, click General in the same window and select Hard disks.

Can the desktop show free space all the time?

Yes. With disk icons on the desktop, click the desktop, choose View › Show View Options, and select Show item info. Each disk's icon then shows its size and how much is free underneath, and the figure updates as you work.

It makes a good everyday gauge. Before a very large copy, check the free space in Disk Utility instead, which leaves purgeable space out.

How do you see how big each folder is?

Finder doesn't add up folder sizes in list view by default, since counting large folders takes time. To turn it on for a folder, open it, choose View › as List, then View › Show View Options, and select Calculate all sizes. Click the Size column heading to put the largest first.

For a single folder, select it and choose File › Get Info. Finder counts everything inside and shows the size when it finishes, which can take a while for a folder with many files.

Why does Get Info show two sizes for a file?

Get Info shows a size such as "4,213,940 bytes (4.2 MB on disk)". The first number is how much data the file holds. The second is the space it actually takes on the disk.

The two can differ a lot. A compressed file takes less on disk than its contents. A sparse file, such as a virtual machine's disk image, can claim to be huge while taking a fraction of that. An APFS clone shares its space with the original until one of them changes, yet each copy shows the full size.

That's why adding up folder sizes, in Finder or any tool that doesn't account for clones and sparse files, gives a number that doesn't match the disk's used space.

Check storage in Disk Utility

Disk Utility is the most technical of macOS's views. It lists free space and purgeable space as separate figures, which makes it the one to check before a large task. In Finder, choose Go › Utilities, then double-click Disk Utility.

What do Used, Other Volumes and Free mean?

Select your startup volume in the sidebar. A bar at the top of the window shows three figures:

• Used: the space the selected volume takes.
• Other Volumes: the space every other volume in the same container takes.
• Free: the space nothing is using.

In the details below the bar, Available can read like "79.69 GB (5.06 GB purgeable)", the same way Get Info shows it.

How do you see purgeable and free space separately?

Select the volume and click the Info button in the toolbar. The list that opens includes Volume capacity, Available space (Purgeable + Free), Used space, Purgeable space and Free space.

Apple describes purgeable space as space macOS can free when needed by removing files, and notes that you can't remove those files yourself. The Free space line is what's open right now.

Why does your disk show several volumes?

Choose View › Show All Devices to see the whole structure: the physical drive, the container on it, and the volumes inside the container. On a current Mac, macOS is installed on a volume group: one volume for the system files, named Macintosh HD, and one for your data, named Macintosh HD - Data or just Data.

What you see	What it is	Can you use its space for files?
The physical drive	The SSD itself	Not directly; it holds the container
The container	The APFS partition all volumes share	Its free space is shared by every volume
Macintosh HD	macOS's read-only system volume	No; only macOS updates change it
Macintosh HD - Data or Data	Your files, apps, settings and caches	Yes; this is where your files go
Preboot, Recovery and VM	Startup files, macOS Recovery, and swap	No; macOS manages them

Your own files all land on the data volume. The system volume stays about the same size between updates, so when your Mac fills up, it's the data volume that grew.

Can you see local snapshots here?

Yes. Choose View › Show APFS Snapshots, then select your startup disk's volume. A list at the bottom of the window shows each snapshot with its name and date. The names of Time Machine's local snapshots start with com.apple.TimeMachine.

Snapshots hold on to files you've deleted or changed since they were taken. No folder shows that space, which is one reason the used space can be larger than everything you can find. The guide to Time Machine's local snapshots explains when they go away by themselves.

How do you check storage when your Mac won't start up?

If your Mac won't finish starting up, you can still check its storage from macOS Recovery, which has its own copy of Disk Utility.

On a Mac with Apple silicon, turn it off, then press and hold the power button until you see "Loading startup options". Click Options, then Continue. On an Intel-based Mac, turn it on and immediately hold Command and R until you see an Apple logo or a spinning globe.

If asked, select your startup disk and a user whose password you know.

Choose Disk Utility in the Recovery window and select your volume. It shows the same used and free figures as it does normally, so you can see how close to full the disk is before deciding what to do.

Other places that show storage

A few more screens look like storage figures, and some of them aren't. Knowing which is which saves a lot of confusion.

Is Activity Monitor's Disk tab about storage?

No. The Disk tab counts how often your Mac reads from and writes to the disk, and how much data moves. It says nothing about how full the disk is.

The Memory tab has one storage-related figure: Swap Used, the space on your startup disk that macOS uses as extra memory. It's counted in System Data, and restarting your Mac clears it.

Is iCloud storage the same as your Mac's storage?

No. iCloud storage is space on Apple's servers, starting at 5 GB with every Apple Account, and it's checked in a different place: open System Settings, click your name at the top of the sidebar, click iCloud, then Manage.

The two affect each other. Store in iCloud and Optimize Mac Storage move files from your Mac into iCloud, so they free Mac storage by using iCloud storage. If iCloud is full, those settings can't help.

How do you check an external drive?

Storage settings covers only your internal disk. For an external drive, use Finder or Disk Utility: select the drive in the Finder sidebar and choose File › Get Info, or select it in Disk Utility and click Info.

Get Info also shows the drive's Format, which matters here. A drive formatted as ExFAT, for example, has no APFS snapshots or clones, so its used space is simply the files on it, plus the drive's own Trash.

What about the command line?

Command-line tools report storage too, in their own units, some of them in binary gigabytes. Everything in this post can be done in Finder, System Settings and Disk Utility, and their figures are the ones Apple's documentation explains.

What each storage number means

The same few words appear on every screen, and they don't always mean the same thing. This table gathers them in one place.

Term	Where you see it	What it means
Capacity	Get Info, Disk Utility, System Information	The size of the disk or volume as macOS formats it
Used	Every view	Space taken by files, from the selected volume or the whole disk
Free	Disk Utility, System Information	Space nothing is using, right now
Available	Finder, Storage settings, About	Free space plus purgeable space
Purgeable	Get Info and Disk Utility, in brackets or on its own line	Space macOS can free by itself when something needs it
Other Volumes	Disk Utility	Space other volumes in the same container take
On disk	Get Info for a file or folder	Space an item really takes, as opposed to the data it holds

What is the difference between free and available?

Apple puts it plainly in its storage guide: free space is physically open space on the disk, while available space includes free space and purgeable disk caches. Space can be both available and used at the same time.

Purgeable space usually comes from Time Machine's local snapshots, from iCloud files macOS can download again, and from caches apps have marked as safe to drop. The purgeable space guide has the details.

Why is your Mac's capacity smaller than what you paid for?

Two reasons. Drive makers, Apple included, count a gigabyte as 1,000,000,000 bytes, and Apple's own specifications add "actual formatted capacity less". Formatting the drive and storing the operating system both take some of it before you save a single file.

On one Mac sold with 512 GB of storage, for example, the container's capacity reads 494.4 GB. The system volume, macOS Recovery and the other system volumes then share that container with your files.

Why does the same disk look smaller in some apps?

Because some apps count in binary units. Apple's article on how storage is measured gives both: a decimal gigabyte is 1,000,000,000 bytes, and a binary gigabyte is 1,073,741,824 bytes. Current versions of macOS count in decimal, as drive makers do.

A tool that counts in binary shows every size about 7% smaller. Nothing is missing; it's the same number of bytes in a bigger unit.

• 256 GB drive238.4 GiB
• 512 GB drive476.8 GiB
• 1 TB drive931.3 GiB
• 2 TB drive1,862.6 GiB
• 4 TB drive3,725.3 GiB
• 8 TB drive7,450.6 GiB

Arithmetic from Apple's definitions: 1 GB is 1,000,000,000 bytes and 1 GiB is 1,073,741,824 bytes. Formatting and macOS's own volumes take more on top.

Why don't used and free add up to the capacity?

In Disk Utility, the selected volume's used space and the free space don't add up to the capacity, because the other volumes in the container take the rest. That's what Disk Utility's Other Volumes figure shows.

In Storage settings, the categories may not add up either. Some space belongs to no file you can see, such as snapshots, and the figures can change while it's still counting.

Why the numbers disagree, with a worked example

The reasons are always the same handful: purgeable space, local snapshots, clones and sparse files, other volumes, and folders an app isn't allowed to read. The storage numbers guide linked above explains each. Here's what they look like on one real Mac.

A worked example on one 512 GB Mac

These figures come from one 512 GB Mac running macOS 27, read at the same moment. Your own figures will differ; the pattern won't.

What was measured	Figure	Why it's that size
The storage it was sold with	512 GB	Decimal gigabytes, before formatting
The container's capacity	494.4 GB	The drive as formatted
Your data volume, used	363.4 GB	Files, apps, settings and caches
The system volume, used	14.1 GB	macOS itself, read-only
Startup, Recovery and swap volumes	40.9 GB	macOS manages them
Free	74.6 GB	Only what's open right now
Available	79.7 GB	Free plus 5.1 GB of purgeable space

Add the used volumes and the free space and you get 493 GB; the last 1.4 GB is the container's own bookkeeping. Finder would show about 79.7 GB available, while Disk Utility's free space and System Information both show 74.6 GB. None of the figures is a mistake.

Which number should you trust?

For day-to-day use, available space is the right figure. It's what macOS will give you once it frees purgeable space, which it does by itself when something asks for room.

Before something big, such as a macOS update, a large download or a video export, look at free space in Disk Utility. A task that checks for room can stop before macOS has freed purgeable space, even when Finder shows plenty available.

Why is used space larger than all your files?

When you add up your folders and get less than the used figure, the difference is usually space no folder shows: local snapshots, swap, and the other volumes. Folders your account can't read, such as other users' home folders and some apps' private data, are missing from the total as well.

When you get more than the used figure, it's usually clones, hard links or sparse files counted in full.

When to check, and what to do with the answer

Checking storage is only useful when it leads somewhere. A quick look tells you whether you have room for what you're about to do, and which part of the disk is worth a closer look.

How often should you check?

It's common to check only when macOS warns that the disk is almost full, which is late. A look every month or two, or before anything large, catches growth while it's still easy to deal with.

Note the three largest categories each time. A category that has grown since last time is where to look first, and it's often not the one you'd guess.

Why does storage keep changing by itself?

Several things grow and shrink without you saving anything. If you use Time Machine, it takes a local snapshot about every hour and keeps each one for 24 hours. Swap grows with heavy apps and resets when you restart. Caches grow with use, and iCloud downloads files when you open them.

Storage settings also recalculates each time you open it. A System Data figure that drops overnight usually means snapshots or swap were cleared, not that anything went wrong.

What should you do with what you found?

Match what you see to its usual cause, then deal with that one thing. This table covers the common cases.

What you see	What it usually means	Where to go next
Finder shows plenty, an update says not enough	The space is purgeable, not free	Check free space in Disk Utility
Deleting files frees nothing	They're in the Trash, or a snapshot holds them	Empty the Trash; check snapshots
System Data is very large	Snapshots, caches, swap or developer files	The System Data guide
Documents is very large	Videos, disk images and archives you've kept	Sort by size and last accessed
iOS Files is large	Old iPhone and iPad backups	Delete backups of devices you no longer own
Other Users & Shared is large	Another account's files, or a deleted user's	Check with them, or an administrator

When you're ready to make room, the guide to freeing up space on a Mac goes through each category in order.

What does the warning that your disk is almost full mean?

When space runs low, macOS shows a notice that your disk is almost full and suggests saving space by optimizing storage. Apple doesn't document the exact point at which it appears.

Treat it as a prompt to check free space, not available space, because the two can be far apart by then. A macOS update, a large download or a video export each need room while they work, and can stop when it isn't there.

How the app does it

Wombit is a native Mac app that shows what's using your storage, explains every item in plain language, and clears it safely: Trash first, undoable and logged. It runs on macOS 26 or later, on Apple silicon and Intel Macs.

Its space meter, in the app and in the menu bar, is meant to be honest about the figures above: it shows what's available and how much of that is really free. The menu bar item shows the available space as text all day. Click it for the meter and, while a macOS update is waiting, whether it fits.

The scan covers the whole disk or any folder, reading only names, sizes and dates, at about 240,000 items a second on an M4 Pro. Hard links and APFS clones count once, the way macOS counts space, so nothing is counted twice.

Folders macOS didn't let it read are listed, not skipped, so you know which numbers are incomplete. File names and paths never leave your Mac.

System Data, explained splits that one number into named buckets, such as local snapshots, caches, logs and swap, and shows how much it couldn't explain instead of hiding it. Items get one of four levels: Safe, Usually safe, Review first and Managed by macOS. Snapshots and swap are Managed by macOS: explained, never moved.

The analyzer, the map, the space meter and System Data explained are free. Cleanup, the Apple Data actions, Time Machine snapshots and What Changed, which shows what grew since last week or your last scan, are 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.