Timestamp a Document Online

Need to timestamp a document online and prove its date and time? BlockchainSign records a SHA-256 fingerprint of your file on the Ethereum blockchain, giving you a trusted timestamp that proves the document existed at that moment — verifiable by anyone, with no software to install.

How to timestamp a document (incl. PDF)

Upload your file or paste text — the SHA-256 hash is generated locally in your browser.
We write the hash to Ethereum — creating a permanent, trusted timestamp.
You receive a lifetime certificate — with the transaction ID and an Etherscan link.

Works for a PDF, image, contract, source code, archive or plain text. Full verification steps are on the how it works page.

Trusted timestamp

The blockchain proves exactly when your file's fingerprint was recorded — no central time authority needed.

Online, no install

Timestamp a document straight from your browser. Nothing to download or set up.

Provably unchanged

Any change to the file changes its hash, so the timestamp also proves the document hasn't been altered.

Why a blockchain timestamp?

Local file dates and ordinary timestamp servers can be changed or can disappear. A blockchain timestamp is public and permanent: your certificate stays verifiable on Etherscan indefinitely, independent of any single provider — including us.