Hash locally
Your browser calculates the file's SHA-256 fingerprint. The file is not uploaded.
Timestamp or verify a file.
No upload. No account. Your browser hashes the file locally.
- ✓Files stay local
- ✓Standard OpenTimestamps proof
- ✓Anchors to Bitcoin
Create a ProofStamp
Choose a file
ProofStamp calculates the file's SHA-256 fingerprint locally with two independent methods. The file never leaves this device.
✓ File ready
Ready to timestamp
Two independent SHA-256 checks match.
See fingerprint
Only a blinded fingerprint is sent to OpenTimestamps. Your file stays on this device.
Start overTimestamp proof created
Save your ProofStamp receipt
Save the receipt now. Bitcoin anchoring can take a few hours. You can close this page and check again later.
Bitcoin anchoring is still pending. This ProofStamp is not Bitcoin-verified yet.
Independent OpenTimestamps proof
This .ots proof is stamped directly against the original file SHA-256. Download it and pair it with the original file in standard OpenTimestamps tools.
- Calendars accepted
- Proof SHA-256
Verify a ProofStamp
Check a file and its receipt
Choose the two files you received. ProofStamp checks the file locally, then checks the timestamp.
Files stay on this device. They are not uploaded to ProofStamp.
Verification result
Timestamp status
File matches the receipt
The exact file SHA-256 matches the one recorded in this ProofStamp.
File not checked
You checked the receipt only. Add the original file to verify the file itself.
Bitcoin timestamp verified
The OpenTimestamps proof has a Bitcoin attestation verified by the browser check.
Bitcoin timestamp still pending
The ProofStamp is valid so far. The Bitcoin attestation is not available yet.
Keep this receipt and check again in about 3 hours. You can close this page.
The timestamp evidence is complete for this browser verification path.
- Bitcoin block
- Block time
Technical details
- File SHA-256
- Timestamped file SHA-256
- Bitcoin block hash
- Verification method
- OpenTimestamps + Blockstream raw block header
For new ProofStamps, use the original file together with the downloaded .ots proof on OpenTimestamps.org. Legacy Manifest-v1 receipts use the prefilled verifier link instead.
Browser verification is a convenience check. It verifies the OpenTimestamps Bitcoin attestation against a raw block header fetched through Blockstream. It is not equivalent to independently validating Bitcoin consensus with your own Bitcoin Core node.
ProofStamp confirms exact file bytes and timestamp evidence. It does not prove authorship or whether the contents are true.
How it works
File → SHA-256 → OpenTimestamps → Bitcoin.
Timestamp the fingerprint
OpenTimestamps timestamps that exact SHA-256 and later anchors it to Bitcoin.
Verify anywhere
Use ProofStamp with the file + receipt, or use the original file + .ots proof with OpenTimestamps.
What a ProofStamp does not prove
It does not prove who created a file, whether its contents are true, or when the file was originally created.
Independent verification
New ProofStamps timestamp the file SHA-256 directly. Download the .ots proof and verify it with the original file using OpenTimestamps.org, the OpenTimestamps CLI, or your own Bitcoin Core node.
Older Manifest-v1 ProofStamp receipts remain supported by this app, but their .ots proof timestamps the legacy Manifest commitment rather than the raw file hash.
Open the official OpenTimestamps verifierRead the independent verification instructions.