Despite rumours that Time Capsules had lost support in macOS Tahoe, those still backing up to them have discovered they continue to work, at least to existing backup stores. I’m very grateful to Michael for telling me that Tahoe no longer lets you start a new backup on a Time Capsule, nor it appears to any other store requiring HFS+ (Mac Extended) format.

Time Capsule support is expected to end with macOS 26 Tahoe, as macOS 27 is unlikely to support AFP any more, so those Intel Macs compatible with Tahoe can continue backing up to Time Capsules until they’re replaced. Apple remains intentionally vague about this, stating only that AFP “won’t be supported in a future version of macOS”, and has been even less clear about support for backup stores on HFS+.

Apple’s documentation implies that has been dropped already. Since Big Sur, it has stated: “APFS or APFS Encrypted disks are the preferred format for a Time Machine backup disk. If you select a new backup disk that’s not already formatted as an APFS disk, you get the option to erase and reformat it. If the disk is a Mac OS Extended format disk that contains an existing Time Machine backup, you aren’t asked to erase and reformat the disk.” However, “Time Machine still supports backups on Mac OS Extended format (Journalled), Mac OS Extended (Case-sensitive, Journalled), and Xsan formatted disks.”

Other support documents are even less helpful. This one doesn’t even mention HFS+, while another, dated 5 December 2025 and detailing backup disks you can use with Time Machine, concentrates on AFP and implies that HFS+ remains fully supported on Time Capsules.

Unfortunately, in macOS Tahoe, the moment you erase your Time Capsule to start a fresh backup series, Time Machine considers that’s a new backup disk, and wants it to be in APFS format. As that’s not possible, it refuses, stating “Time Machine can only be used if it contains existing Time Machine backups for this Mac.”

Michael found an ingenious workaround on his MacBook Air M2, by installing Sequoia in its own container, starting up from that, and then creating the new backup store on his Time Capsule. When he restarted his Mac in Tahoe, Time Machine was perfectly happy to start a new backup set, as it already existed.

From this we can only conclude that macOS Tahoe:

• fully supports Time Machine backups using AFP,
• fully supports Time Machine backups to Time Capsules with backup stores already formatted in HFS+,
• but refuses to create a new backup store on a Time Capsule,
• also refuses to create a new backup store on local storage formatted in HFS+, but insists on reformatting that to APFS.

I don’t believe for a moment this behaviour is a bug, but is an intentional limitation that Apple hasn’t documented. While I have been warning since July 2021 that you should replace any Time Capsules, as they won’t be supported for much longer, this abrupt change is unwarranted.

If you’ve upgraded to macOS Tahoe and erase your Time Capsule’s backups, you’ll be unable to store any new backups on it, unless you revert to Sequoia. This is yet another compelling reason not to upgrade to macOS 26.