Disk Health reads the SMART data your Mac’s disk reports. It never writes anything to the disk.
- Wear — how much of the drive’s rated write endurance has been used. SCleaner estimates the remaining life from how fast this grows.
- Spare blocks — reserve space the drive uses to replace worn cells. A falling value is worth watching.
- Temperature — current drive temperature.
- Media errors and unexpected power losses — counts reported by the drive.
Each finding comes with a plain-language explanation. If SCleaner reports a serious problem, back up your data first.