Step by step
Short answer: don't delete anything. Move it, hold it, and look at your archive before you commit. Every irreversible photo loss involving a duplicate finder happens because deletion and identification were the same action.
The walkthrough below uses DuplicateFinder Pro, which is ours. The principle isn't ours and applies to whatever you use: nothing should leave your archive on the same click that found it.
Scanning and the full reports are free, so you can run everything on this page and see the result before deciding anything.
A duplicate finder makes two separate claims, and people usually only hear the first one.
The first claim is these two files have identical contents. That one can be proven, and good software proves it by reading both files rather than comparing their names.
The second claim is and therefore you don't need this one. That is not a fact about the files. It depends on which drive you're keeping, which folder your catalog points at, whether the second copy is a backup you meant to have, and whether the thing you're about to delete is genuinely duplicated or merely similar. Software can't know any of that.
So the safe shape of this job is: let the software make the first claim, keep the second one for yourself, and make sure the gap between them is reversible. In practice that means files get moved and held, not deleted, and you get to look at your archive before anything becomes permanent.
DuplicateFinder Pro isn't code-signed. A signing certificate is an annual cost that hasn't been taken on yet, and without one Windows describes the publisher as unknown. That's a statement about paperwork, not about the file — but it produces warnings that deserve a straight explanation rather than a "just click through".
Get-FileHash .\DuplicateFinderPro_Setup_v1.5.exe -Algorithm SHA256. It should match character for character. If it doesn't, don't run it — download it again, and if it still differs, email support.
If any of that leaves you uncomfortable, that's a reasonable place to land. Run the fingerprint check, and if you're still not comfortable, don't install it. Clicking through warnings you don't understand is a worse habit than skipping one piece of software.
If you're cleaning up a single archive — one drive, one folder tree — this is the whole flow.
Comparing separate folders or drives is a different tab, and it's easy to miss. Scan Target in the left rail takes one location. Cross-location comparison lives in Folder Duplicates, which has its own list and its own scan button.
Add locations with Add Folder / Drive — folders or whole drive roots, two or more, on any connected drives. No naming convention or folder structure is assumed: every file under each location is checked by content, at any depth, against every file under the others.
The rule that matters is stated on screen above the scan button: the copy in the first folder listed is the one kept. Matching copies in the folders below it are the ones flagged. There's no drag to reorder — to change which copy wins, select a folder, Remove Selected, and add it back in the order you want. Then click Scan for Duplicate Files, not Start Scan.
If you're consolidating two external drives specifically, there's a longer piece on how to compare two external drives — including the order of operations that keeps the drive you're retiring safe.
Results are split by kind across the tabs: RAW and JPG pairs in the same folder, RAW and JPG pairs across folders, duplicate JPGs, duplicate RAWs, duplicate videos, GoPro audio, and folder comparisons.
Every row carries a Role — whether it's the copy being kept or a copy being flagged — plus the file, its size, its folder, and a Match column naming which test found it. Select any row to preview the file. A running Recoverable figure, group count and flagged count sit along the bottom.
Three tests run in order, cheapest first. Size, which eliminates almost everything without reading a byte. A partial fingerprint of the first and last megabyte of whatever survived. Then a full read of whatever's still standing. Only a full-content match is reported as a duplicate — never a matching name, never a matching timestamp.
Export the CSV before you move anything. It costs nothing and it's your record of what the drive looked like on the day you did this.
RAW files sharing a filename but not byte-identical are grouped anyway, so you can see them side by side. Those rows read stem+size in the Match column rather than md5, and if the sizes differ by more than 5% they're marked Review instead of being flagged. The software is telling you it found something related and is declining to decide. Look at those yourself.
These get confused, and the confusion is the dangerous part.
Quarantined files carry a 24-hour hold. Use it. Open your archive in whatever you actually work in — Lightroom, Bridge, Explorer — and look at it properly before emptying anything. The moment you regret a cleanup is almost always the moment after it finishes.
Restore is one click and returns each file to its exact original location. If a file's origin is on a drive that isn't connected, the app names that drive, leaves the file safely in quarantine, and offers to continue with the rest — it won't redirect anything to a path that merely looks close enough. Each file is written in full before its quarantine record clears, so an interrupted restore can't leave a half-written file in your archive.
Restore is never locked. Not without a licence, and not after a refund. Files this software moved are always files you can move back.
Scanning, the Storage Map and the full CSV and HTML reports are free, with no account. You can run every scan on this page and see exactly what was found and how much space it would recover. The $34 licence is only needed to move flagged files into quarantine.
No. Nothing is deleted at any point by the software. Flagged files are moved to a quarantine folder on the same drive and recorded. Emptying quarantine is a separate action you take yourself, and restore and permanent delete are never locked behind the licence.
Lightroom will show it as missing until you restore it, which takes one click within the 24-hour hold or after it. The app excludes Lightroom's own working folders from scanning but has no knowledge of which photos are catalogued — catalog awareness is planned, not shipped.
Flagging marks rows so they can be moved in bulk afterwards; the file is untouched until you click Move Flagged to Quarantine, and quarantine is a folder rather than a bin. The label is more alarming than the behaviour.
No. It looks at RAW photos, exported JPGs, MOV and MP4 video and GoPro WAV audio, and ignores everything else on the drive. It is not a general-purpose duplicate file cleaner — it is built for the one archive where a wrong deletion is unrecoverable.
It depends on the archive, but the staged tests mean most files are eliminated on size alone without ever being read. A multi-terabyte pass can run for hours; it's checkpointed, so it can be paused and resumed rather than restarted.
The free scan tells you how much of your drive is genuinely redundant before you commit to anything. On a 931 GB drive here, it found 78.8 GB of second copies — worth knowing either way.