Mac Apps

Make sure your Time Machine backups aren’t corrupted

Time Machine backups are a great safety net. You should always create a Time Machine backup before making any changes at the operating system level, such as installing a beta version of macOS, and before applying any experimental or unsupported changes, such as using a third party app to alter your system font.

However, it is possible for Time Machine backups to become corrupted – this can happen naturally over time, but it can also happen maliciously, for example a hacker may use your Time Machine backups as a way of getting viruses onto your Mac.

Time Machine has a built-in feature that can help you identify whether a backup has changed since it was created. This ‘verify backups’ feature compares the checksum generated when the backup was created, to the current checksum – if these digits are different, then this is a sign that the backup has become corrupted, or been modified in some way.

In this article, I’ll be showing you how to use this feature to verify the integrity of any backup made to a server, AirPort Time Capsule, or a drive that’s either connected directly to your Mac, or to an AirPort Extreme Base Station. This feature works with both encrypted and unencrypted backups, and for all backups created after macOS 10.11.

While you’ll typically use this feature to verify the integrity of a backup before restoring it, this feature can also be handy if you encounter problems with restoring a particular Time Machine backup, as it gives you a way of testing whether this problem is being caused by the backup itself.

Verify the integrity of any Time Machine backup

The easiest way to verify the integrity of a backup, is to use the Time Machine icon in your Mac’s menu bar. If you haven’t added this icon to your menu bar, then do so now:

  • Click the ‘Apple’ logo in the menu bar.
  • Select ‘System preferences > Time machine.’
  • Select the ‘Show Time Machine in menu bar’ checkbox.

Then, to compare the checksums:

  • Make sure the backup you want to verify is currently available, for example if it’s stored on an external drive then make sure this drive is connected to your Mac.
  • Select the Time Machine icon in your Mac’s menu bar.
  • Press and hold down the ‘Option’ key on your keyboard.
  • Select ‘Verify Backups’ from the dropdown menu that appears.

Time Machine will then run its checksum test, and display a dialogue if it discovers any discrepancies between these two checksums.

Verifying backups from the Terminal

If you’re comfortable with issuing Terminal commands, then you can also verify the integrity of a backup using macOS’ built-in tmutil utility:

  • If you backup to an external drive, then make sure this drive is currently available.
  • Launch your Mac’s Terminal, by opening a Finder window and navigating to ‘Applications > Utilities > Terminal.’
  • Type the following command into the Terminal:

tmutil verifychecksums /path-to-your-backup

  • Press the ‘Enter’ key on your keyboard.

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About the author


I've been a passionate evangelist for Apple and the Macintosh throughout my working life, my first love was a Quadra 605 working with a small creative agency in the south of Norfolk UK in the mid 1990's, I later progressed to other roles in other Macintosh dominated industries, first as a Senior graphic designer at a small printing company and then a production manager at Guardian Media Group. As the publishing and printing sector wained I moved into Internet Marketing and in 2006 co-founded which grew to become one the top 200 visited sites in the US (according to Quantcast), at its peak receiving over 15 million visits per month. For the last ten years I have worked as an Affiliate and Consultant to many different business and start ups, my key skill set being online marketing, on page monetisation, landing page optimisation and traffic generation, if you would like to hire me or discuss your current project please reach out to me here.

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