Mac Disk Almost Full: Find What Is Using Space and Free It
A warning that your startup disk is almost full is easy to ignore until the Mac slows down, an update refuses to install, or you cannot save a file. The good news is that most of the space is usually taken by a handful of things, and you can find them in a few minutes.
This guide is written for Mac, with notes for Windows at the end in case you manage both kinds of computer. Nothing here requires special software.
Step 1: See what is using the space
Start with the built-in storage report, because it shows you where to look before you delete anything.
- Click the Apple menu in the top left corner and open System Settings.
- Choose General, then Storage. On older versions of macOS, choose About This Mac, then the Storage tab, then Manage.
- Wait a moment while the colored bar fills in. It breaks your disk into categories such as Applications, Documents, Photos, Messages and System Data.
Look for the biggest block of color. That is where your effort will pay off most. Each category has an information button or a Manage option that lets you review the items inside it.
A note on System Data: this category includes caches (temporary files that apps store to work faster), logs, and other items macOS manages itself. It can be large and it is not very specific. Do not try to hunt it down and delete things by hand. Work on the other categories first, then restart the Mac, which often lets macOS tidy up some of this on its own.
Step 2: Remove the easy wins
These are the safest places to recover space, roughly in order of how often they help.
Empty the Trash. Files you delete stay in the Trash and still use space until you empty it. Right-click the Trash icon in the Dock and choose Empty Trash. This cannot be undone, so glance inside first.
Check the Downloads folder. Open Finder, click Downloads in the sidebar, and sort by Size by clicking the Size column heading (switch to List view first if you do not see columns). Old installers, disk images ending in .dmg, and large zip files are usually safe to remove once the software is installed.
Review large files. In the Storage screen, open Documents. macOS lists your largest files and folders. Videos, old backups and forgotten project files tend to appear here. Delete only what you recognize, and move anything you want to keep to an external drive.
Uninstall apps you no longer use. Open Applications in the Storage screen, sort by size, and remove programs you have not touched in a long time. Drag the app to the Trash, then empty it.
Clear out Messages attachments. If you use Messages, the Storage screen has a section for it. Old photos and videos sent in chats can add up quietly.
Step 3: Deal with photos, mail and backups carefully
Some items deserve a little more thought before you remove them.
Photos. Your photo library may be the largest single thing on the Mac. If you use iCloud Photos, you can turn on the option to optimize Mac storage, which keeps smaller versions on the computer and the full versions online. Be sure your photos are actually uploaded before changing this. If you do not use iCloud Photos, copy the library to an external drive before removing anything.
Mail. Mail downloads attachments to your Mac. In the Storage screen, the Mail section shows how much space they use. Removing them from the Mac does not delete the original messages on the mail server in most setups, but check how your account is configured if you are unsure.
Old iPhone or iPad backups. If you once backed up a phone to this Mac, those backups can be very large. In the Storage screen, look for iOS Files or a similar entry and review what is listed. Only delete backups for devices you no longer own, or ones you have since backed up elsewhere.
Time Machine snapshots. If you use Time Machine, macOS keeps temporary local snapshots on the disk and removes them automatically when space runs low. You do not need to manage these by hand.
What to leave alone
Resist the urge to delete anything in the System or Library folders, or any folder you do not recognize. Third-party cleaning tools that promise to free space automatically are not needed for this job, and some remove files that apps depend on. Everything above can be done with the tools already on your Mac.
If you are unsure about a file, leave it. Moving it to an external drive is a safer choice than deleting it.
A note for Windows
The idea is the same on a Windows PC, only the screens differ. Open Settings, then System, then Storage. Windows shows categories and lets you review Temporary files, which you can remove with the Clean up option. Storage Sense, on the same screen, can be switched on to empty the Recycle Bin and clear old temporary files on a schedule. Check the Downloads folder and uninstall unused apps from Settings, then Apps, just as you would on a Mac.
Keep it from filling up again
Once you have freed some room, aim to keep a comfortable amount of free space, since a nearly full disk can make the computer sluggish. Make a habit of emptying the Trash and Downloads folder every month or so, and keep large photo and video collections on an external drive or in cloud storage you trust. A quick look at the Storage screen every few months will tell you when it is time to tidy up again.
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