How to Safely Extract Mac ‘SSD Terabytes Written’ (Check Hard Drive Lifespan)

Unlike old mechanical hard drives that could spin for decades, modern Solid State Drives (SSDs) have a finite lifespan. Every single time your Mac writes data to the SSD (downloading a file, saving a video, or just browsing the web), it slightly wears down the flash memory cells. This metric is known as “Terabytes Written” (TBW).

If you buy a used Mac, or if you have been heavily editing 4K video for years, your SSD might be approaching its physical death. macOS does not display this critical health information anywhere in the graphical settings menus. To find out exactly how much life your SSD has left, you must extract the raw SMART (Self-Monitoring, Analysis, and Reporting Technology) data using the Terminal.

How to Safely Extract Mac SSD Terabytes Written

You must use the `smartmontools` utility (installed via Homebrew) to read the hardware sensors.

1. Open the Finder, go to Applications, open the Utilities folder, and double-click Terminal.
2. If you do not already have the Homebrew package manager installed, you must install it first by pasting this command and pressing Enter: /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
3. Once Homebrew is ready, type the following command to install the SMART hardware reader: brew install smartmontools
4. Next, we must find the exact hardware identifier of your main SSD. Type: diskutil list
5. Look for the main internal drive (usually labeled /dev/disk0).
6. To extract the exact amount of data written to the drive over its entire lifetime, type this final command (replace disk0 if yours is different) and press Enter: smartctl -a /dev/disk0

The terminal will output a massive wall of text. Scroll down to the bottom section labeled SMART Log. Look for the line that says Data Units Written. It will display a massive number followed by the exact terabyte translation (e.g., [45.2 TB]). Most modern Mac SSDs are rated for at least 150 to 300 TBW. If your number is approaching the manufacturer’s limit, you must immediately back up your data, as the drive is nearing the end of its physical lifespan.