OpenTimestamps and .ots Files Explained: Pending vs Confirmed Proof

What is inside an .ots file, why your proof shows as pending, how to make it confirmed and how to verify it, all in simple language.

1. What is OpenTimestamps?

OpenTimestamps is a free, open standard that uses the Bitcoin blockchain to create a date-stamped proof for a file. You don't have to trust any company, account or subscription. The date is whatever is written in the Bitcoin blockchain, and it cannot be changed.

The proof comes in a small .ots file, which you keep safe along with your original file.

2. How does it work? (simple version)

1. Fingerprint: A SHA-256 hash of your file is created.
2. Calendar server: Only that hash (32 bytes) is sent to the public OpenTimestamps calendar servers.
3. Batching: The calendar server combines the hashes of many people into a single value (a Merkle tree).
4. Bitcoin: That single value is placed in a Bitcoin transaction.
5. Block confirmation: Once the transaction is included in a Bitcoin block, the date is locked in.

3. What is inside an .ots file?

An .ots file is like a receipt. It contains:

• Your file's SHA-256 hash
• The path through the calendar server (operations) that links your hash to a Bitcoin transaction
• An attestation: at first the calendar server's pending attestation, and once confirmed, the Bitcoin block's attestation

It is usually 1-2 KB in size and does not contain your file at all. That makes it safe to send to someone.

4. Pending vs Confirmed: what's the difference?

A newly created proof is always pending right after you make it. This is not a mistake, it is a normal part of the process.

5. How to turn a pending proof into a confirmed one

1. After a few hours (or the next day), open opentimestamps.org.
2. Add your original file and your .ots file there.
3. If the Bitcoin confirmation has arrived, the site upgrades the proof and shows the confirmed date.
4. Download the upgraded .ots file and replace the old pending file with it.

There is a command line for developers too. After pip install opentimestamps-client, you can run ots upgrade file.ext.ots and ots verify file.ext.ots. Full verification usually needs a Bitcoin node or a block explorer, so opentimestamps.org is easier for most users.

6. How to verify: our tool vs opentimestamps.org

In the Verify Proof tab of Proof of Original, add the original file and the .ots. The tool:

• recalculates the file's SHA-256 and matches it against the hash inside the .ots,
• tells you whether the proof has a Bitcoin attestation or is still pending.

This tool does not read the Bitcoin blockchain itself. For the exact date of the block, add both files on opentimestamps.org, which checks the full chain. This way you don't have to trust a single website.

7. Common errors and how to fix them

• "No match": The file is different from the original. It may have been re-saved, compressed, edited or renamed with changes. Use the untouched original.
• "Not a valid OpenTimestamps file": The wrong file was chosen. Only add a .ots file.
• "Hash matches, proof is still pending": All good. Wait for the Bitcoin confirmation and then upgrade.
• Lost .ots: You can create a new proof, but it will carry the new date, not the old one. That is why you should keep your .ots on both Drive and a pen drive.

8. Limits of this proof

• It proves that this exact file existed by this date. It does not prove who created the file.
• It is not a copyright registration. In India, copyright arises as soon as you create the work and registration is optional, but in a dispute you still need evidence. A timestamp can serve as supporting evidence.
• How much weight this proof carries in a court or on a platform depends on the case and the country. This is not legal advice, so talk to a lawyer for a serious case.

The complete step-by-step workflow for creators: How to Prove Your YouTube Video Is Original. And the basics of hashes: What Is a SHA-256 Hash?.