How to check a copy is perfect: verify files byte for byte
A copy that finished without an error message isn’t necessarily a perfect copy. Bad sectors, a flaky cable, a drive that dropped out for a second, or a copy that was interrupted and restarted can all leave files missing, truncated or quietly different.
Compare the copy against the original. Retrova’s Verify checks the files you recovered at three depths: names and sizes, a spot check of each file, or every byte. It repairs mismatches from the original and saves SHA-256 checksums so you can re-check later. For other copies, built-in command-line tools do the job.
Three levels of checking
| Mode | What it compares | Use it when |
|---|---|---|
| Quick | Every file exists, with the same size | You want a fast sanity check of a big copy |
| Spot check | Size, plus the start, the end and 8 random 1 MB pieces of every file | Catching copies that were cut short or filled with zeros, fast |
| Every byte | Every byte of every file, plus SHA-256 checksums | The copy is the one you’ll keep, or the original is about to be wiped |
Verify with Retrova
- After recovering files, choose Check a copy is perfect on the home screen, or go to Verify.
- Pick the recovery you want to check, then how thorough to be: Quick, Spot check or Every byte.
- Retrova lists anything missing, different or unreadable, with the reason for each.
- Click Repair to re-copy just the files that don’t match from the original. Only the copy is ever written.
- Export the results as CSV, and keep the SHA-256 manifest next to the copy so you can check it again in a year.
Doing it by hand
If you prefer the command line, these built-in tools compare files too:
- macOS or Linux:
shasum -a 256 fileprints a checksum for each file; matching checksums mean identical files. For whole folders,diff -rq original copylists files that differ. - Windows:
Get-FileHash file -Algorithm SHA256in PowerShell, orfc /b original copyin Command Prompt for a byte-by-byte compare.
Use these for copies made outside Retrova, such as a Finder or Explorer copy between two folders. They work, but over thousands of files they’re slow to read through, and they don’t repair anything.
Get Retrova
Free and open source for macOS 11+ and Windows 10/11. No account, no recovery limit, and it never writes to the drive you’re rescuing.
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Is a checksum the same as a byte-for-byte compare?
For practical purposes, yes. Matching SHA-256 checksums mean the files are identical. Retrova’s Every byte mode compares the bytes directly and also writes SHA-256 checksums to a manifest, so you can re-check the copy later without the original.
Can Retrova verify a copy made by Finder, Explorer or rsync?
Not yet. Verify checks copies Retrova made from a drive or disk image. For other copies, use shasum, Get-FileHash or fc as shown above.
What happens with files the original can’t read?
They’re reported separately as unreadable in the original, so you know the problem is in the source, not in your copy.