Mac only
Startup disk full on Mac
Your startup disk is the drive macOS runs from. When it fills up, the whole Mac suffers. Here is what to check.
The startup disk is your Mac’s main drive, usually called Macintosh HD. If it is almost full, you may see a warning, slow apps or failed updates.
Check how full it is
Open System Settings, General, Storage. The bar shows used and free space for the startup disk. Aim to keep some room free, because macOS needs space to work and to update.
What is System Data?
System Data is the grey part of the bar. It holds caches, logs, app support files and other things macOS keeps. It is normal for it to take some space, but it can grow to tens of gigabytes. Local Time Machine snapshots can count here too, and macOS removes them when it needs the room.
What to clear first
- Your own big filesDownloads, videos, disk images and old projects are the most common cause. Start there, because these are files you can judge yourself.
- TrashEmpty it. Deleted files still take space until you do.
- Unused appsRemove apps you no longer open. Some keep large files in their own folders.
- Old device backupsIf you backed up an iPhone or iPad to this Mac long ago, old backups can be very large. Check Storage settings, or in Finder open your device and choose Manage Backups.
- A restartRestarting clears temporary files and can free some space.
Avoid apps that promise to clean System Data in one click, and do not delete files in the Library folder by hand. You can break an app or lose settings.
Move files to the cloud you already pay for
If you already pay for Google Drive, Dropbox, OneDrive or another storage, you have space you are not using on your Mac. DriveMyMac shows that storage as a drive in Finder. Files stay in the cloud and take no space on your Mac until you open them.
- Add your storageOpen DriveMyMac, choose Add storage and sign in with your cloud. The drive appears in the Finder sidebar.
- Drag a folder inDrag big folders from your Mac into the drive. Check that they are there, then delete the originals on your Mac.
- Open files when you need themA file downloads when you open it. Choose Keep on this Mac for files you want offline.
- Private by designYour files go straight from your Mac to your own cloud. DriveMyMac never sees or stores them. The sign-in stays in your Mac’s Keychain.
Works with Google Drive, Dropbox, OneDrive and more. See all supported clouds. DriveMyMac is not a backup: keep a second copy of files you cannot lose.
Questions
Why is System Data so large on my Mac?
It holds caches, logs, snapshots and other files kept by macOS and apps. Restart, remove big files you no longer need and check again. If it stays huge, ask Apple Support.
Can I make the startup disk bigger?
Not on a modern Mac, because the storage is built in. You make room by moving files off the disk, for example to an external drive or to your cloud.
Can I keep my Documents in the cloud?
Yes. With DriveMyMac you add your cloud as a drive in Finder and move folders into it. They take no space on your Mac until you open them.
Does DriveMyMac see my files?
Your files go straight from your Mac to your own cloud. DriveMyMac never sees or stores them.
Do I pay for storage through DriveMyMac?
No. You keep paying your own cloud for its storage. DriveMyMac is a one-time payment per Mac, with no subscription.
Pay once. Keep it.
$5.99 lifetime at launch, then $19.99 lifetime. One time, per Mac.