External drives · Caring for a drive
Do I need to defragment an external SSD or hard drive on a Mac?
Short answer: No. SSDs don't benefit from defragmenting and it only adds wear; macOS has no defragment tool and doesn't need one. For a slow hard disk, keep some free space on it and check its health with First Aid instead.
No for SSDs, and rarely for hard disks. An SSD reads every location equally fast, so defragmenting gains nothing and only adds wear. macOS doesn't offer a defragment tool and doesn't need one for normal use.
A heavily used, nearly full hard disk can get slower over time, but the practical fix is to keep free space on it rather than defragment. If a hard disk is noticeably slow, check its health with First Aid first — slowness is more often a sign of age than fragmentation.