Backup Checksum

Backup Checksum checks whether your backups really match your originals. It scans a folder, calculates a checksum for every file, and saves the results to a checksum list. You can compare that list with another one later, or search it for duplicates.

It has three tools, each on its own tab:

• Calculate checksums. Pick a folder and Backup Checksum works through every file in it, including subfolders, then writes each file’s path, size and checksum to a result file. Reading and calculating run in parallel on several threads, so it can go as fast as your local disks or your network allow. You can skip Windows Thumbs.db files, and any file that can’t be read goes into a separate error log.
• Compare checksums. Load two checksum lists, for example one from your original drive and one from your backup, and Backup Checksum reports what differs. You choose which warnings you want: Files missing from either list. Files with the same size but a different checksum (likely corrupted). Files with the same checksum but a different size. Files where both the checksum and the size differ.
• Find equal files. Check a file, a folder or another checksum list against one or more existing checksum lists to find identical files. This shows you duplicates, or whether something is already backed up. You can log only matched files or only unmatched files. You can also turn on equality verification to confirm matches against the actual files, and leave out matches where a file finds itself.

Checksum lists are plain text files, so you can read them, keep them alongside your backups and compare them again years later.

Written together with Johan Rydh.