Checksum tools and manifests

Checksums are portable evidence about file bytes. Archive Witness can calculate them independently of a registered archive and can reconcile external checksum manifests with catalog files.

Calculate or compare

Use Checksum tools… when you need archive-independent checksum work.

• Calculate checksums produces checksum observations for selected files.
• Comparison modes use Check integrity because they compare current bytes with supplied checksum evidence.

The algorithms selected under Settings → Checksum algorithms are the starting selection for Calculate checksums, including calculations launched from File Explorer. You can adjust the selection in each Checksum tools window. Verification against pasted or sidecar evidence uses the algorithm identified by that evidence.

A calculated value is not automatically accepted as a saved reference.

On Windows 11, right-click an individual file in File Explorer and open the Archive Witness submenu:

• Hash with Archive Witness opens checksum calculation for that file and starts the calculation.
• Verify with Archive Witness loads a recognized checksum sidecar when the sidecar itself is selected. When an ordinary file is selected, Archive Witness automatically loads its one same-named .sha256, .b3, .blake3, .sha512, .sha1, or .md5 sidecar. One unambiguous comparison starts immediately. If none or several exist, choose the intended checksum evidence in the window; its file picker starts in the ordinary file's folder.

These commands are installed and removed with the MSIX package. They operate on one file at a time and do not add the file to an archive. If Archive Witness is already running, the command brings that process forward and opens Checksum tools there.

The installed app can also open .b3, .blake3, .md5, .sha1, .sha256, and .sha512 files directly. After fresh-install onboarding, Archive Witness offers to open its own page in Windows Default Apps, which lists only the file types registered by Archive Witness. Windows requires you to choose which of them it should open. Double-clicking an assigned checksum file opens Checksum tools and starts verification when its target resolves unambiguously.

Choosing or typing a different source file clears the previous visible result immediately. If that exact file version was already calculated in the open window, starting the calculation again may reuse the session cache and identifies that reuse explicitly.

Import historical manifests before replacing them

If you have checksum manifests from before a move, rename, recovery, or catalog migration, apply that evidence before creating a new baseline. Historical evidence may answer whether current bytes survived unchanged in a way a newly created checksum cannot.

Reconcile path differences deliberately

A manifest path that no longer matches the current filesystem is not failed checksum evidence. Review prefix mappings, digest matches, and manual mappings so that path/name drift is resolved explicitly rather than by editing historical data to fit the present layout.

Export for portability

After establishing an important accepted baseline, export portable checksum manifests to separate healthy storage. The manifest remains useful even if the Archive Witness catalog is unavailable.