TDS File Reference v1 — public format, CC0 1.0
Published 2026-09-25. https://thedollscout.com/verify-file

Purpose: compare the bytes of a local file with a sender-provided reference.
This is a file-integrity check, not a blockchain, certificate, reputation score,
signature, malware check, proof of authorship, acceptance or trusted timestamp.
Anyone can make a reference. A substituted file AND reference will match.
Obtain the reference from the sender through a channel you trust.

Canonical English link:
https://thedollscout.com/verify-file?via=recipient#tds-file-v1=SHA256.BYTES
German and Chinese links use /de/verify-file and /zh/verify-file.
SHA256: exactly 64 lowercase hexadecimal characters, SHA-256 of exact file bytes.
BYTES: base-10 byte count, no leading zeros, from 0 through 20971520 (20 MiB).
The fragment contains no file name, content, project note, ID or timestamp.
Hashes are not encryption: holders can test whether a file matches the reference.
The browser does not include the fragment in an HTTP page request. A copied URL
can still be stored by messaging apps, clipboard tools, browser history or recipients.
TDS scripts must not transmit the fragment or digest in analytics events.

Independent verification:
1. Keep the original file and full reference URL. No TDS account is needed.
2. Calculate SHA-256 and exact byte length. Both must match the reference.
3. Optional: save https://thedollscout.com/document-assets/verify-file-cli.mjs
   and inspect its source. Run with Node.js 20+ (no packages or network needed):
   node verify-file-cli.mjs ./my-file 'FULL_REFERENCE_URL'
   Exit 0 = match; 1 = different; 2 = invalid input/read failure.
4. Other implementations may use any correct SHA-256 library. TDS is not required.

Known-answer test: UTF-8 bytes abc (no newline), size 3:
ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad
Renaming the file does not change this result; adding a newline does.
Never run an untrusted file just to check it.

For Bitcoin-backed time proofs, OpenTimestamps is a separate open protocol:
https://opentimestamps.org/
TDS does not submit hashes to calendars, create .ots proofs, or claim anchoring.
Keep a completed timestamp proof and verify it independently if using that service.