Offline Transaction Builder

Build an EIP-1559 transaction, sign it offline with a local key, get the raw hex — optionally broadcast.

browser → public RPC handles secrets

You are online

Keys and mnemonics are generated and processed only in this browser tab; nothing is sent anywhere, nothing is stored, and the page has no analytics. You may want to turn off the internet before using this tool: the site caches itself on first visit, so this page keeps working offline. For wallets that will hold real funds: go offline, generate, write the secret down on paper, then close the tab. Prefer a hardware wallet for anything serious. Anything you copy can be read by other apps with clipboard access.

Sender private key

To (empty = contract creation)

Value (ETH)

Data (hex) — build calldata with the ABI encoder

Nonce

Gas limit

Max fee (gwei)

Priority fee (gwei)

Air-gapped flow

Fill in the fields, sign with the network disconnected, copy the raw hex, and broadcast it from any machine — here, via cast publish, or an explorer's "broadcast raw tx" page. Nonce and fees must be fetched (or known) beforehand.