macOS 26 has locked up my AirPort Time Capsule

For the past ten years, my Apple Time Capsule has faithfully backed up my Mac. I’ve gone through several upgrades over the past ten years — my current machine is an M3 Max MacBook Pro — and I’ve never had a problem with the Time Capsule. It’s been one of the most reliable devices I’ve ever owned and I’ve barely had to think about it since I bought it in 2016.

Until recently, that is I don’t know the exact date, but I installed macOS Tahoe 26.2 sometime in late 2025. I was hoping it would fix the persistent problems I was having with Spotlight, but otherwise I didn’t think much of it until I got a message from Time Machine that my backup drive was full.

Over the years I’ve occasionally had minor problems with Time Machine backups, but these were usually fixed by simply running the backup again. This was a new persistent error that seemed to indicate something was wrong with my backup system. So I started researching the problem and the process ended up crashing my Time Capsule.

Time keeps turning

Apple introduced Time Capsule in 2008 as “a backup device that automatically and wirelessly backs up everything on one or more Macs.” It was a new concept at the time, combining an AirPort base station with a “server-grade” hard drive. It was basically a personal NAS drive before there were personal NAS drives.

I’ve owned a few over the years, and before Apple finally discontinued the Time Capsule in 2018, I bought one of the last models ever made, the AirPort Time Capsule 802.11ac (WiFi 5) Mini Tower. It’s been running ever since.

I have a 2TB Time Capsule backing up a Mac with 250GB full, so space has never been an issue. Plus, I’ve been using the same MacBook since Sonoma, so there’s no reason why it should suddenly run out of space. When I upgrade to a new OS, I normally wipe all backups and start over, and I keep most of my files backed up to a 2TB iCloud Drive, so the physical space should be more than enough.

So I went into my AirPort settings to check my Time Capsule. But it wouldn’t accept my password, the same password I’ve been using for at least five years and saved in my password manager.

OK, that was weird, but I still flagged it as user error. I reset my Time Capsule with a paper clip and changed my password. I checked the space and it said there was less than one gig available. Also strange. My Mac is nowhere near 2TB, I don’t keep old backups, and Time Machine is supposed to automatically delete the oldest backups to free up full disk space to keep running.

Unfortunately, there’s no way to find out what’s filling up Time Machine’s “Data” file, so I’m left with one option: Wipe the drive.

Tahoe’s Revenge

Apple announced last summer that it would no longer support AirPort or other Time Capsule drives for Time Machine backups with macOS 27, which will be available later this year, due to outdated support for the Apple Filing Protocol. So I was already preparing for the day when I had to retire my 10 year old drive to stay on the latest version of macOS.

I agree that 10 years is a long time to use any device, let alone a 3.5 inch SATA drive. But I didn’t expect any problems with the Tahoe. I figured I could wipe the drive and simply start over while I collect the eight or so months of backups until macOS 27 arrives in September.

Foundry

At this point I probably should have put two and two together and realized something was wrong. But rather naively I pushed.

Erasing the Time Capsule was simple. The Drives tab in AirPort Utility has a “Quick Erase” option that only takes a few seconds. I clicked through the standard “This cannot be undone” dialog box, but got no warnings specifically about the Tahoe. The light changed from orange to green, showing that I now had 2 TB of space, and everything seemed fine.

However, when I went to set up the drive in Time Machine settings, I got a new message: “Data can only be used if it contains existing Time Machine backups for this Mac. The next major version of macOS will no longer support Time Capsule drives for Time Machine backups.”

Foundry

I already knew the second part. The first part was information that would be useful before I wiped the drive. I searched for a solution and came to the conclusion that my Time Capsule backup drive is basically a brick. To use it, I would have to downgrade to the Sequoia, back up my computer, upgrade to the Tahoe, and keep backing up until the drive fills up again, at which point I’d be right back where I started.

Finding a solution

To recap: Either a bug or a feature in macOS Tahoe 26.2 caused my Time Machine backups to take up all available space on my Time Capsule drive, rendering it unusable to wipe. I’m still not sure if the password issue was Tahoe related, but I suspect it was. (A reader reached out to say he had a similar problem with oversized backups in macOS 26.2, but the problem was fixed this week with the 26.3 update. Shame I didn’t wait.)

But that’s okay—since Apple has already announced that Time Capsule won’t work with future versions of macOS, I’m left with a retro paperweight.

So after ten years of trouble-free backups with Time Capsule, I’m left to find a new solution. Macworld has a roundup of the best external hard drives or SSDs for wired Time Machine backups, as well as the best NAS drives. There are some great options out there, but I want to find the best replacement for Time Capsule, so I’ll be testing a few wireless drives on my Mac with Time Machine to try and find the most affordable alternative. So stay tuned.