On a modern Mac the SSD is built into the logic board, so it can’t be swapped out on its own. Knowing how worn it is tells you how much to rely on it, and how seriously to take your backups.
The quick check: SMART status
Hold Option, open the Apple menu and choose System Information, then select NVMExpress. S.M.A.R.T. status: Verified means the drive reports no failures.
That’s a pass or fail, not a measure of wear. A drive can be Verified and still have used most of its rated life.
The detailed check: wear and data written
The drive keeps its own health log. macOS doesn’t show it, but the free, open-source smartctl tool reads it. With Homebrew installed:
brew install smartmontools
smartctl -a disk0Look for these lines:
- Percentage Used: the drive’s own estimate of how much of its rated life is used. It can pass 100%; drives often keep working well beyond their rating.
- Data Units Written: how much has been written over the drive’s life.
- Available Spare: reserve blocks left to replace worn ones. A value at or below its threshold is a warning.
- Critical Warning: anything other than 0 means back up now.
Why swapping wears the SSD
When a Mac runs short of memory, macOS writes memory to the SSD (swap) and reads it back. On a Mac with 8 GB that’s often under memory pressure, that can add up to a great deal of writing. Keeping pressure low, and keeping enough free disk space, spares the drive as well as speeding things up.
What to do with the result
- Under 50% used: plenty of life left.
- 50 to 90%: fine for now; make sure Time Machine or another backup is running.
- Over 90%, low spare, or any critical warning: keep backups current and plan for the Mac’s replacement or a logic board repair.