What the disk gauge in NotchStar shows
The disk ring in the NotchStar System tab shows how full your startup volume is, as a percentage of its total size. It counts space that macOS can reclaim by itself, such as purgeable files, as free, so it can look emptier than Terminal says.
How the number is made
NotchStar reads the total capacity of the volume mounted at / and the capacity macOS reports as available for important usage. That second figure is the one Finder uses, and it includes space the system would free if it needed to. The ring shows one minus free divided by total.
Why it can disagree with Terminal
The command df -h /System/Volumes/Data prints the plain used and available figures, without the reclaimable part. On a Mac with a lot of purgeable data the ring reads lower than df does. Neither is wrong, they answer different questions: how much could I use, and how much is physically free right now.
Colours
The ring turns orange above 65 percent and red above 85 percent.
What it does not cover
- Only the startup volume. External drives and other volumes are not in this ring. Open the Disk tab and its Overview to see free space for every drive. See how to check free space and eject drives.
- It does not say what is using the space. For that, use the Disk tab’s Space section, or read how to free space without a cleaner app.
The tool is described on the System stats feature page, and the cleanup side on the Disk feature page.
