Free space alone doesn’t tell you anything; the rate it disappears does. DeltaFree reads your APFS containers through diskutil, stores a point each time you run it, and after a fortnight of samples plots the trend and does the arithmetic for you — 700 GB free, 14 GB a week, fifty weeks. It watches every container the Mac can see, so a change in the slope shows up before the disk does. Free, macOS 14.6 and later.