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How to Check and Format Disks with Disk Utility on Mac

Tap each step to follow along in order.

  1. Launch Disk Utility

    Open "Disk Utility" from the Utilities folder inside Applications, or launch it directly with Spotlight search.

  2. Select the disk you want to work on

    From the list on the left, choose either your internal disk or a connected external drive that you want to check or format.

  3. Run First Aid to check for errors

    Click "First Aid" in the toolbar, then click "Run" to scan the disk's file system for errors and automatically repair what it can.

  4. Erase (format) an external drive

    Click "Erase" at the top, enter a name, and choose a format suited to how you'll use it -- APFS for Mac-only use, or exFAT if it also needs to work with Windows.

  5. Confirm the partition scheme

    When formatting, double-check that the scheme is set to GUID Partition Map so you don't accidentally erase the drive with the wrong setup.

  6. Eject the disk safely when finished

    Once formatting or checking is complete, eject the external drive from Finder before unplugging the cable, to avoid corrupting the data.

What Disk Utility is actually good for

Disk Utility is a tool built into every Mac that you can use to format an external drive for a specific purpose, or to check a disk for file system errors and repair the ones it can fix on its own.

Formatting an external drive erases everything on it

Because erasing a disk removes all of its data with no way to get it back, always copy anything important off the drive somewhere else first. If you're not sure which format to pick, APFS makes sense for a drive that will only ever be used with a Mac, while exFAT is the safer choice if it also needs to plug into a Windows PC.

Frequently Asked Questions

If I erase a disk, is the data on it gone for good?

Yes -- erasing removes all the data on the disk, so make sure anything important is backed up elsewhere first.

Should I pick exFAT or APFS?

APFS is the better fit for a drive you'll only use with a Mac, while exFAT is the more compatible choice if the same drive also needs to work with a Windows PC.