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/ Function Selector

Function

Function selector (4 byte encoding)

/ Selected Tool

Function Selector

Calculate Solidity function selectors

■ 01

Selector In Seconds

Paste a Solidity function signature and get the 4-byte selector immediately, without bouncing to another lookup tool.

■ 02

Built For Contract Work

Useful for calldata inspection, ABI debugging, interface work, and everyday smart-contract development tasks.

■ 03

Copy-Ready Output

The result is ready to paste into scripts, tests, deployment flows, and contract tooling the moment you generate it.

/ Code■

/ 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, toFunctionSelector } from 'viem';

// Calculate function selector (4 bytes) from function signature
function getFunctionSelector(functionSignature: string): string {
  // Hash the function signature with keccak256
  const hash = keccak256(toBytes(functionSignature));

  // Take first 4 bytes (8 hex characters + 0x)