ether-js

Lightweight Ethereum utility library for Node.js and browser.

Zero dependencies. Includes a pure-JS keccak256 implementation — no @noble/hashes, no ethers, nothing extra.

Features

• formatEther — Convert wei to human-readable ETH strings
• parseEther — Parse ETH strings to wei (BigInt)
• isAddress — Validate Ethereum addresses
• toChecksumAddress — Convert to EIP-55 checksummed address
• keccak256 — Compute keccak256 hash (pure JS, no deps)
• Zero dependencies — Lightweight, tree-shakeable
• TypeScript — Full type definitions included

Installation

npm install ether-js

Usage

const { formatEther, parseEther, isAddress } = require('ether-js');

// Convert wei to ETH
console.log(formatEther(1000000000000000000n)); // "1.0"

// Parse ETH to wei
console.log(parseEther('1.5')); // 1500000000000000000n

// Validate address
console.log(isAddress('0x742d35Cc6634C0532925a3b844Bc9e7595f2bD18')); // true

API

formatEther(wei: bigint | string | number): string

Convert wei to ether, with 18 decimal places.

parseEther(eth: string | number): bigint

Convert ether string to wei as BigInt.

isAddress(address: string): boolean

Returns true if the string is a valid Ethereum address.

toChecksumAddress(address: string): string | null

Returns EIP-55 checksummed address or null if invalid.

keccak256(data: string | Uint8Array): string

Compute keccak256 hash of input data. Accepts hex strings (with or without 0x prefix), plain strings (UTF-8 encoded), and Uint8Array.

License

MIT