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See what a transaction does before you sign it

Paste the transaction your wallet or a site asks you to sign — or an existing tx hash. We replay it on a private fork of the chain and tell you, in plain words, what leaves and arrives, which approvals it grants and which contracts it calls. Nothing is signed or broadcast; no wallet is connected.

A transaction your wallet will send (or an existing tx hash) — replayed on a private fork.

Input

From / to / value / calldata, as shown by your wallet's “advanced / data” view. Addresses only — never keys.

Fills in a real example on Ethereum: giving the Uniswap router UNLIMITED permission to spend USDC — a common request that the result will warn you about. It is only simulated; nothing is sent.

Where do I find these values?
  1. Open the transaction in your wallet before you confirm it (MetaMask: the “Hex” or “Data” tab; Rabby: “View raw”; most wallets: “Advanced”).
  2. From = your own wallet address. To = the contract or person the transaction goes to.
  3. Calldata = the long 0x… text in the Data / Hex tab. Copy all of it.
  4. Value = the amount of the network coin (ETH / BNB) being sent. Usually 0 for token actions.
  5. Don't confirm in the wallet until you've read the result here. Never paste a private key or seed phrase.
Words used here
Calldata
— the instructions inside a transaction — which function is called and with what values.
Approval
— permission for a contract to move your tokens later. “Unlimited” means all of them, until you revoke it.
Fork
— a private copy of the blockchain on our server, where the transaction runs without touching the real one.
Revert
— the transaction would fail; nothing moves, but you'd still pay a fee.
Raw transaction
— an already-signed transaction as one long 0x… text. We only replay it; we never send it.

Native coin sent with the tx, in ETH (e.g. 0.05). Leave empty for 0.

0x… — the “data” / “hex” field. Empty for a plain coin transfer.

Read-only: the fork is local to our server and is thrown away. A signed raw tx you paste is decoded and replayed on the fork only — it is never sent to the network. Never paste a private key or seed phrase anywhere.