Migration Assistant left me with duplicates of everything

Why migrations create duplicates

Migrations don't copy a perfect mirror of your files. They combine what was already there with what you brought over, and the result is a pile of near-identical copies. The common culprits:

• Merged user folders. Migration Assistant and manual copy both merge the old home folder into the new one. If a folder with the same name already existed, macOS keeps both instead of overwriting — that's where the "Folder (2)"-style names come from.
• Re-downloaded files. A fresh Mac pulls down apps and downloads again, so you can end up with the same installer or archive in both your Documents and your Downloads.
• Doubled photo and video exports. Exporting a photo library to a folder, then importing that folder into a second library, duplicates the files without you noticing.
• External-drive redundancy. Files you backed up to a drive before the move are now both on the drive and on the new Mac. That's not always a mistake — sometimes you want the copy — but it's why duplicates are scattered.

None of this means the migration failed. It means you have a cleanup task, and the safe way to do it is deliberate, not wholesale.

Check safely before deleting anything

Start with the built-in tools. They're free, they're on your Mac, and they let you confirm a duplicate is really a duplicate before you touch it.

1. Look for the obvious first

Open a Finder window and look for "Folder (2)", "Folder copy", "Name 2", or files with identical names in adjacent folders. Sizes in Finder's list view are a first pass, but equal names and equal sizes don't prove the bytes match. Treat Finder as triage, not proof.

2. Compare checksums with shasum

A checksum is a fingerprint of a file's bytes. Two files with the same checksum are byte-for-byte identical. Open Terminal and run:

shasum -a 256 "old/path/file.mov" "new/path/file.mov"

If both lines show the same hash, the files are identical. If the hashes differ, they are not the same file — keep both. This is the fastest way to settle the question for a specific pair of files, and it's how you should verify anything you're about to remove.

3. Use Finder smart folders to group candidates

A smart folder is a saved search that keeps itself updated. To find candidate duplicates by name or kind, do a Finder search, then hit the Save button to pin it to the sidebar. You can add rules for file kind, name, and date. A smart folder won't find byte-exact copies for you, but it puts every likely pair in one place so you can compare them one at a time.

4. Know what "safe to delete" means before you delete

A file is safe to delete when you have verified a matching original exists somewhere you intend to keep, and you've confirmed nothing else depends on that particular file. Until both are true, it isn't a duplicate — it's a file you might need.

Why bulk-deleting with a "duplicate finder" is the risky step

An app that claims to find duplicates is convenient, but the danger is almost never finding the duplicates. It's what happens in the seconds after you hit "delete". The real failure modes:

• Wrong keeper. "Keep the newest" sounds sensible, but the newest copy isn't always the one with your edits. A photo library's edited version can be the one you want, even if it isn't the newest timestamp.
• Broken app internals. A single library file (a photo library, a mail archive, a game save) is one item that's really a whole bundle of files inside. Deleting the "duplicate" library can leave an app pointing at a now-broken bundle, even when the copy you kept looks fine on disk.
• No undo. When a tool sends files to the Trash and you empty it — or when it deletes directly to free space fast — there's no recovering what went. A wrong bulk delete is hours of work to undo, or it isn't undoable at all.

The risk isn't the duplicate detection. It's acting on a list you didn't individually verify, with no way back. Anything that deletes by default is asking you to accept that risk all at once.

A safe cleanup workflow

You don't have to trust any tool for this — the process itself keeps you safe. It slows the delete down, which is exactly what you want.

1. Inventory. List where the candidates live: the home folder, the external drive, each restored backup. Write down which locations are "keepers" (the places you'll rely on) and which are "leftovers" (the migration remnants).
2. Decide keepers, not deletions. For each pair or group, pick the file you're keeping and why. "The one in Documents" or "the edited export" beats "the biggest one".
3. Move, don't delete. Move the losers into a single folder you create — for example a folder named Migration-Removal-Review on your Desktop. Keep it there while you work.
4. Verify. Open a few of the files you moved to confirm the ones you kept are the right ones. Run shasum -a 256 on anything important. Confirm the apps you use still open their libraries.
5. Only then empty. After you've lived with the move for a bit — a day or two — and nothing has broken, empty that review folder to the Trash, then empty the Trash. That's the moment deletion actually happens, and it's now an informed one.

Where Archivist Sort fits

If the manual pass works for you, use it. When the pile is too big to review by hand, Archivist Sort applies the same careful workflow to the whole drive — with the safety rails kept in place:

• Quarantine, not delete. Approved moves go to a quarantine; nothing is deleted by execution.
• Receipts. Every action is journaled with checksums.
• Byte-verified rollback. One command restores originals and verifies every byte.
• Local-only. No cloud calls, no accounts, no telemetry. Files never leave your Mac.
• Free scan, free plan. Download, scan, and see the full plan at no cost. $29 once is executing that plan with quarantine, receipts, and byte-verified rollback.

Archivist Sort is designed around the same idea as the manual workflow above: inventory, review, approve, quarantine, rollback. It doesn't guess, and it doesn't delete by default. You still decide what's kept; it just makes reviewing thousands of files tractable.

It's built to back the claims it makes — see how it works on the product page.