calldata decoder

paste a transaction's input data and an ABI, and decode the function call into its 4-byte selector, name, signature, and typed arguments — for any EVM contract, entirely in your browser.

abi

[
  {
    "type": "function",
    "name": "name",
    "stateMutability": "view",
    "inputs": [],
    "outputs": [
      {
        "name": "",
        "type": "string"
      }
    ]
  },
  {
    "type": "function",
    "name": "symbol",
    "stateMutability": "view",
    "inputs": [],
    "outputs": [
      {
        "name": "",
        "type": "string"
      }
    ]
  },
  {
    "type": "function",
    "name": "decimals",
    "stateMutability": "view",
    "inputs": [],
    "outputs": [
      {
        "name": "",
        "type": "uint8"
      }
    ]
  },
  {
    "type": "function",
    "name": "totalSupply",
    "stateMutability": "view",
    "inputs": [],
    "outputs": [
      {
        "name": "",
        "type": "uint256"
      }
    ]
  },
  {
    "type": "function",
    "name": "balanceOf",
    "stateMutability": "view",
    "inputs": [
      {
        "name": "account",
        "type": "address"
      }
    ],
    "outputs": [
      {
        "name": "",
        "type": "uint256"
      }
    ]
  },
  {
    "type": "function",
    "name": "allowance",
    "stateMutability": "view",
    "inputs": [
      {
        "name": "owner",
        "type": "address"
      },
      {
        "name": "spender",
        "type": "address"
      }
    ],
    "outputs": [
      {
        "name": "",
        "type": "uint256"
      }
    ]
  },
  {
    "type": "function",
    "name": "transfer",
    "stateMutability": "nonpayable",
    "inputs": [
      {
        "name": "to",
        "type": "address"
      },
      {
        "name": "amount",
        "type": "uint256"
      }
    ],
    "outputs": [
      {
        "name": "",
        "type": "bool"
      }
    ]
  },
  {
    "type": "function",
    "name": "approve",
    "stateMutability": "nonpayable",
    "inputs": [
      {
        "name": "spender",
        "type": "address"
      },
      {
        "name": "amount",
        "type": "uint256"
      }
    ],
    "outputs": [
      {
        "name": "",
        "type": "bool"
      }
    ]
  },
  {
    "type": "function",
    "name": "transferFrom",
    "stateMutability": "nonpayable",
    "inputs": [
      {
        "name": "from",
        "type": "address"
      },
      {
        "name": "to",
        "type": "address"
      },
      {
        "name": "amount",
        "type": "uint256"
      }
    ],
    "outputs": [
      {
        "name": "",
        "type": "bool"
      }
    ]
  },
  {
    "type": "event",
    "name": "Transfer",
    "anonymous": false,
    "inputs": [
      {
        "name": "from",
        "type": "address",
        "indexed": true
      },
      {
        "name": "to",
        "type": "address",
        "indexed": true
      },
      {
        "name": "value",
        "type": "uint256",
        "indexed": false
      }
    ]
  },
  {
    "type": "event",
    "name": "Approval",
    "anonymous": false,
    "inputs": [
      {
        "name": "owner",
        "type": "address",
        "indexed": true
      },
      {
        "name": "spender",
        "type": "address",
        "indexed": true
      },
      {
        "name": "value",
        "type": "uint256",
        "indexed": false
      }
    ]
  },
  {
    "type": "error",
    "name": "ERC20InsufficientBalance",
    "inputs": [
      {
        "name": "sender",
        "type": "address"
      },
      {
        "name": "balance",
        "type": "uint256"
      },
      {
        "name": "needed",
        "type": "uint256"
      }
    ]
  },
  {
    "type": "error",
    "name": "ERC20InsufficientAllowance",
    "inputs": [
      {
        "name": "spender",
        "type": "address"
      },
      {
        "name": "allowance",
        "type": "uint256"
      },
      {
        "name": "needed",
        "type": "uint256"
      }
    ]
  },
  {
    "type": "error",
    "name": "ERC20InvalidSender",
    "inputs": [
      {
        "name": "sender",
        "type": "address"
      }
    ]
  },
  {
    "type": "error",
    "name": "ERC20InvalidReceiver",
    "inputs": [
      {
        "name": "receiver",
        "type": "address"
      }
    ]
  }
]

calldata

paste a transaction's input data to decode the call and its arguments against the ABI ·

what is transaction calldata?

every EVM transaction that calls a contract carries an input data field — the calldata. it begins with a 4-byte function selector (the first four bytes of the keccak-256 hash of the function signature) followed by the arguments, ABI-encoded into 32-byte words. decoding it turns that opaque hex blob back into a readable call: which function was invoked and with what values.

how to decode calldata here

paste the contract's ABI (or keep the ERC-20 ABI loaded by default), then paste the full input data — selector plus encoded arguments, whitespace is ignored so explorer copies work. the tool matches the selector against the ABI's functions and decodes each argument by type, including addresses, integers, booleans, bytes, strings, arrays, and tuples. a bare 4-byte selector resolves to its function; a 32-byte value resolves an event topic.

decoding runs locally with viem; nothing is uploaded. to read and write functions, decode revert errors, and look up selectors in one place, open the read · write workbench.