How to find and delete duplicate files on a Mac

Why your Mac fills up with duplicates

Duplicates happen slowly: saving a design twice under different names, downloading a video into Downloads and Documents, or leaving old project clones sitting around after a copy-paste. On a long-lived developer machine, it's not unusual for the duplicate count to hit tens of thousands — and the reclaimable space to reach tens of gigabytes.

Finder's built-in suggestions surface obvious photo duplicates, but it misses files with different names that share the same contents. A copy of report.pdf and report_final.pdf don't look the same to macOS.

The quick Terminal approach

If you want to try it yourself, you can list files and their MD5 hashes:

find ~ -type f -exec md5 -r  + | sort | uniq -d -w 32

That shows groups with matching hashes — but it's slow on big drives, and it gives you nothing to preview or act on. It's useful as a proof-of-concept, not a daily tool.

The better way: content-hash + preview + staging

A proper duplicate finder should hash file contents, group them, show you exactly how many bytes each group would reclaim, and let you preview every file in a group before you decide.

That's what DiskInsight's Duplicate Finder does. On a full Mac scan it found 75,129 extra copies across 22,502 groups — all grouped, previewable, and ready to stage to the Trash with one click.

• Content-addressed: catches copies with different names and in different folders.
• Byte counts per group: you know exactly what's worth your time.
• Everything goes to the Trash — nothing permanent, nothing in the background.

What counts as a duplicate?

• Downloads vs. Documents: a video or PDF saved in both places.
• Project copies: folders copied to "old-project-backup" and never touched again.
• Exported media: photos and videos exported at different sizes or resolutions.
• Build artifacts: compiled binaries checked into a repo and also in DerivedData.

The safe cleanup approach

Always keep one copy of each group. DiskInsight lets you review which copy to keep before staging anything to the Trash. No permanent deletion ever happens automatically — you move to Trash yourself, and can recover from the Trash until you empty it.