TimeMachine is not removing any old backups.

The disk itself is plenty big enough (1TB, backing up a 500GB main drive), and I have (multiple times) reformatted it to start TimeMachine afresh. After about a month, the TimeMachine disk is full. I last formatted the disk August 19th, and now (September 10th) the disk is full. I can see about 490 backup snapshots, give or take every hour.

The TimeMachine disk is an SSD, formatted Mac OS Extended & Encrypted.

What could be causing this and what else could I try to get TimeMachine to thin out backups as it used to?

  • @anki that refers to local snapshots, not snapshots on an external TimeMachine disk. I could manually delete snapshots on the disk, but TimeMachine should be doing this automatically.
    – rowatt
    Sep 10, 2020 at 18:05
  • Time Machine usually 'sticks' if any single file is too large to fit the space left. VM files are primary candidate for that type of issue.
    – Tetsujin
    Sep 10, 2020 at 18:38
  • @Tetsujin understood, but I don't see how this could be due to a single too big file. Even after only 2 days of backups, the hourly backups are not being thinned, and at that point I still have 100's of GB free on the TM disk.
    – rowatt
    Sep 10, 2020 at 18:51
  • So it still has hourly files from more than 24h ago? [It will, of course, have hourlies from yesterday, until midnight tonight] What OS? High Sierra used to do things like this, Mojave is better; I don't have Catalina to test. The usual 'fix' for dodgy TM drives is Disk Warrior, though it unfortunately can't deal with APFS drives yet.
    – Tetsujin
    Sep 11, 2020 at 7:05

1 Answer 1


I gave up trying to fix this directly, but after upgrading to macOS 11, and using the same SSD freshly formatted with APFS - as now supported in macOS 11 - TimeMachine is back to working as it should, with hourly snapshots being cleared out after 24hrs.

I can't say if the upgrade cleared out something corrupted, or if macOS 11 can now deal with the issue I was having, but it did fix things.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .