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/ Smart Contract Method ID Finder

Method ID (4 bytes)

Enter the first 4 bytes of a function selector to look it up

Common Examples

How it works: This tool searches the 4byte.directory database, which maintains a registry of Ethereum function signatures and their corresponding 4-byte method IDs. Click "Search" to open results in a new tab.

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Smart Contract Method ID Finder

Look up smart contract method signatures by their 4-byte method ID

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What is a Method ID?

A method ID (or function selector) is the first 4 bytes of the Keccak-256 hash of a function signature. It's used to identify which function to call in a smart contract transaction.

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How does it work?

4byte.directory 4byte.directory is a community-maintained database of Ethereum function signatures. When you see an unknown method ID in a transaction, you can look it up here to find the human-readable function signatu…

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Sample Cases

Covers ERC-20 transfer, ERC-20 approve, and ERC-20 transferFrom so you can compare common inputs and outputs quickly.

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/ Integration

Source code from the selected tool, shown here alongside the live version on the right.

/ Source Code

TypeScript

typescript

// npm install viem

import { keccak256, toBytes } from 'viem';

// Get method ID (4-byte selector) from function signature
function getMethodId(signature: string): string {
  const hash = keccak256(toBytes(signature));
  return hash.slice(0, 10); // First 4 bytes (8 hex chars + "0x")
}