A practical guide to content-based photo comparison

Why filename matching falls short

Camera imports, editing apps and manual reorganising often change names. A comparison based on paths or filenames can miss identical files under different names and can mistake a same-name file with changed content for a match.

Content hashing takes a different approach: read each file and calculate a digest from its bytes. Fix My Photo Library uses SHA-256 to compare supported photo files in the two folders selected by the user.

What “verified” means here: the source and backup scans completed, every included file was fully hashed, and every unique source content has a match in the backup. A failed read, skipped cloud placeholder or interrupted scan cannot produce a verified result.

Unique content and duplicate counts are separate

Suppose a source folder contains two copies of one image and a backup contains one. The unique content exists in the backup, but the second source copy is not mirrored. The report separates missing unique content from excess source copies, so those two situations are not collapsed into a single yes/no label.

Extra files in a backup are reported separately. They are not automatically deleted: old edits and exports may be intentional.

A careful verification workflow

  1. Choose the source photo folder and the backup folder.
  2. Let enumeration and hashing finish. Do not disconnect a drive during the check.
  3. Read the assurance result and any errors. “Incomplete” is not “verified”.
  4. If content is missing, choose whether to copy the identified source files to a destination outside the source tree.
  5. Run a fresh backup check after copying.

Why a copy is not automatic

A source can change after a scan. Before copying, the app hashes the source again, writes to a unique destination name, verifies the copied hash and refuses to overwrite an existing file. If the source changed, it asks you to run the check again.

Cloud placeholders and reparse-point folders are not silently followed. If the app cannot read all selected content, it does not claim complete verification.

Frequently asked about photo backup checks

Does SHA-256 compare photo appearance?

No. It compares bytes. Two visually identical exports encoded with different metadata or compression may have different hashes. This tool deliberately labels only byte-identical content as a match.

Can an incomplete scan still show useful matches?

Yes, partial matches can be listed for review. They do not establish that every photo is backed up, so the assurance remains incomplete.

Need duplicate cleanup too?

Read the exact duplicate photo review guide to learn how a keeper and a restorable quarantine work.