Major improvements in its plots make this new utility even better for tracking changes in used space, and so forecasting how long backup storage will take to fill.
free space
Snapshots made by Time Machine and tmutil should be purgeable, although sometimes they won’t purge, and aren’t shown reliably as purgeable space. An exploration of bugs and missing documentation.
All APFS volumes in a single partition/container share its free space. How can that be measured? How much could be purged, and how do special file types affect it?
To work out how long you’ll be able to use your present backup storage, you need to know how much space is free now, and the rate at which free space is being used by further backups. This app can forecast that, and more.
As Time Machine has changed, first to back up APFS volumes, then to create backups as snapshots, its needs have changed. This makes it complicated to decide which local snapshots you can delete without affecting its backups.
It was notorious for its crashes and reporting discrepancies, but now it’s incorporated in System Settings it’s more reliable and helpful. But there’s still the problem of System Data.
Why upgrading to Tahoe shouldn’t consume the last free space on your Mac’s SSD, and once it has settled should use little more than currently. How to clear out old snapshots and reduce System Data.
What do you do when you discover your Mac’s Data volume has run out of free space? A guide to working with snapshots, iCloud Drive, and other tricks to salvage your Mac. And how to prevent this from happening again.
Speed up your hard disk by partitioning it so that its innermost 20% remains unused. Reserve space for the SLC write cache on an SSD by limiting the size of volumes.
When it started up after its macOS update, available space on its internal SSD had shot from about 160 GB to nearly 400 GB. Where had all my files gone?
The Eclectic Light Company 