Mac storage basics · Disks, APFS and formats

What is TRIM, and does my Mac use it?

Q: What is TRIM, and does my Mac use it?

TRIM lets the operating system tell an SSD which blocks are no longer in use, helping it keep its speed and wear even. Apple's internal SSDs use it automatically. For third-party SSDs, macOS may not enable TRIM by default; the trimforce command can turn it on, but Apple warns it's at your own risk. Many external SSDs connected over USB don't receive TRIM at all and manage themselves. Check a drive's TRIM status in System Information → NVMExpress or SATA.

Short answer: TRIM tells an SSD which blocks are free so it keeps its speed. Apple's internal SSDs use it automatically; third-party and USB-connected SSDs may not.

TRIM lets the operating system tell an SSD which blocks are no longer in use, helping it keep its speed and wear even. Apple's internal SSDs use it automatically.

For third-party SSDs, macOS may not enable TRIM by default; the trimforce command can turn it on, but Apple warns it's at your own risk. Many external SSDs connected over USB don't receive TRIM at all and manage themselves. Check a drive's TRIM status in System Information → NVMExpress or SATA.

Last reviewed October 1, 2026

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What is TRIM, and does my Mac use it?

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