Verify · Browser-side

Verify OTS Proof

Verify any .ots timestamp proof from any source — including files stamped on opentimestamps.org, this service, or the CLI tool. Verification runs in your browser using the OpenTimestamps protocol. If the proof has been upgraded, the latest .ots will be available for download.

1. Local original file

Drop the original file or choose it from this device

The file is read and hashed in this browser; file contents are not uploaded

2. OTS proof file

Drop .ots file or click to browse

Locally parsed; maximum proof size 4 MiB

1. SHA-256 hash
2. OTS proof file

Drop .ots file or click to browse

Locally parsed; maximum proof size 4 MiB

How it works:
  1. Compute the SHA-256 of your original file (done in browser).
  2. Parse the .ots proof and extract the OpenTimestamps operations.
  3. Attempt to upgrade any pending attestations by contacting calendar servers.
  4. Verify the proof against Bitcoin block explorers.
  5. If verified, displays the Bitcoin block height and timestamp.

Privacy: Your file never leaves the browser — only the proof metadata is sent to public calendar servers and block explorers for verification.