Notarize documents with the Gridcoin blockchain
Stamping a document on the Gridcoin blockchain creates a publicly verifiable record that it existed at a specific time. Any later edit, even a single bit, produces a different hash, so tampering shows up immediately. More about how it works.
To notarize a document or verify it later, drag and drop the file below.
The service is free to use.
- Select file
- Stamp
- Get Results
Drag n drop your file here, or click to select.
Most Recent Stamps
How it works
- Drop a file above. Your browser computes its SHA-256 hash locally, so the document itself never leaves your device.
- The hash is written to the Gridcoin blockchain and timestamped. Once it is in a block, it stays there for good.
- You get a permanent proof URL you can share. It shows the hash and the time it was recorded.
Questions
Does my file get uploaded?
No. Only the SHA-256 hash is sent. The file stays in your browser, so we never see its contents, its name, or its size.
What happens if this site disappears?
Your proof lives on the Gridcoin blockchain, not on our servers. Anyone can check a hash against the chain independently, so the timestamp survives even if stamp.gridcoin.club does not.
How can I check this myself?
Re-hash your file and look the stamp up on a block explorer. The hash sits inside the transaction and the block's time is the proof. Step-by-step guide.
Made with ❤ by @gridcat · Part of Gridcoin Club ↗ · Terms · Testnet ↗