Every modern hard drive and Solid State Drive (SSD) contains built-in self-monitoring hardware known as S.M.A.R.T. (Self-Monitoring, Analysis, and Reporting Technology). This system constantly analyzes the physical health of the drive, tracking metrics like read error rates, temperature spikes, and relocated sectors.
If your Mac is suddenly crashing, running incredibly slowly, or exhibiting kernel panics, checking the S.M.A.R.T. status should be your first diagnostic step. If the status reports a failure, it means the drive is physically dying and you must back up your data immediately before it becomes unrecoverable.
While you can view this status in the graphical Disk Utility app, it is often faster and more reliable to query the hardware directly using a single command in the macOS Terminal.
How to Check S.M.A.R.T. Status in Terminal
To query the drive’s health, we will use the built-in diskutil command-line tool.
- Open the Terminal app on your Mac. You can find it by pressing Command + Space to open Spotlight Search, typing “Terminal”, and pressing Enter.
- Once the Terminal window is open, you first need to identify the exact identifier of your primary hard drive. Type the following command and press Enter:
diskutil listThis command will print a list of all storage devices connected to your Mac. Look at the very top of the list for the section labelled /dev/disk0 (internal, physical). This is almost always your primary internal Mac drive.
- Now that you have confirmed the identifier is
disk0, you can query its specific health status. Type the following command and press Enter:
diskutil info disk0 | grep SMARTUnderstanding the Output
The command will instantly return a single line of text detailing the hardware status.
- SMART Status: Verified — This is the perfect result. It means the drive’s internal sensors have not detected any imminent hardware failures or critical threshold breaches. Your drive is healthy.
- SMART Status: Failing — This is a catastrophic result. The drive has detected mechanical damage or critical SSD cell degradation and is actively dying. Stop using your Mac immediately, connect an external drive, and run a Time Machine backup. The drive could fail completely within days or even hours.
- SMART Status: Not Supported — If you see this, you are likely querying an external USB hard drive or a cheap flash drive. S.M.A.R.T. data cannot natively travel over standard USB protocols on macOS without specialized third-party kernel extensions, so the OS cannot read the health data of external drives.