Message Signer & Verifier
Sign and verify a message with an ECDSA secp256k1 key (Bitcoin/Ethereum’s curve) — in your browser.
🔒 100% in your browser — nothing is uploaded
How it works
Sign a message with a secp256k1 private key — the same curve Bitcoin and Ethereum use — or verify a signature against a public key. The message is hashed with SHA-256 and signed with ECDSA, all in your browser. Use the “New key” button for a throwaway key; never paste a key that controls real funds.
Never paste a private key that secures real funds into any website.
Frequently asked questions
What does signing a message prove?
A valid signature proves the holder of the matching private key signed that exact message — the basis of wallet ownership proofs and authentication.
Which curve and hash are used?
secp256k1 (Bitcoin/Ethereum’s elliptic curve) with ECDSA over a SHA-256 hash of the message.
Is my private key safe?
Signing happens entirely in your browser and nothing is uploaded — but treat any key you paste online as compromised. Use the generated throwaway key for testing.