Finding specific things

Finding duplicate files on a Mac

Updated 2026-07-31 · 6 min read

Duplicate finders are a crowded and slightly disreputable category. You can do most of the job with tools already on your Mac, and understand what you are deleting.

Decide what 'duplicate' means first

This matters more than the tool:

• Same name — fast to find, but two files called notes.txt are usually different.
• Same name and size — a good practical signal, and cheap to check.
• Same content hash — definitive, and expensive, because every byte must be read.

Most regret comes from deleting on the first definition while believing the third.

By content, in the Terminal

This finds genuinely identical files in a folder tree:

find ~/Documents -type f -exec md5 -r {} \; | sort | uniq -d -w 32

md5 -r prints the hash then the path; sorting groups identical hashes; uniq -d -w 32 shows only those whose first 32 characters — the hash — repeat.

Accurate, and slow in proportion to how much data you have, since every file is read in full.

A faster two-stage approach

Files of different sizes cannot be identical, so filter by size first and hash only the groups that collide:

find ~/Documents -type f -print0 | xargs -0 stat -f "%z %N" | sort -n | awk '{
  if ($1 == prev) print prevline "\n" $0; prev = $1; prevline = $0 }'

Then hash only those candidates. On a large library this is dramatically quicker.

By name, across the whole machine

The question is often narrower than "find all duplicates" — it is "do I have another copy of *this* file". A complete filename index answers that instantly, including copies on drives that are not plugged in. Everywhere binds that to ⌘D: select a file, press it, and every other copy of that name appears, with same-size matches ranked first because that is the distinction that decides whether deleting is safe.

Before you delete anything

• Check the paths, not just the names. Two identical files in Documents and on a

backup drive are not redundancy to be cleaned up; that is the backup working.

• Beware files inside app packages and libraries — Photos keeps originals and edits that

look like duplicates and are not.

• Move to Trash rather than deleting outright, and leave it a week.

Common questions

Are duplicate files safe to delete?

Only after checking where each copy lives. Copies on a backup drive or inside an app library are usually meant to be there.

What is the fastest way to compare two specific files?

cmp -s file1 file2 && echo identical — it stops at the first difference rather than hashing both in full.