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A collection of utility functions for Ethereum.


To obtain the latest version, simply require the project using npm:

npm install @ethereumjs/util


This package contains the following modules providing respective helper methods, classes and commonly re-used constants.

All helpers are re-exported from the root level and deep imports are not necessary. So an import can be done like this:

import { hexToBytes, isValidChecksumAddress } from '@ethereumjs/util'

Module: account

Class representing an Account and providing private/public key and address-related functionality (creation, validation, conversion).

// ./examples/account.ts

import { Account } from '@ethereumjs/util'

const account = Account.fromAccountData({
  nonce: '0x02',
  balance: '0x0384',
  storageRoot: '0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421',
  codeHash: '0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470',
console.log(`Account with nonce=${account.nonce} and balance=${account.balance} created`)

Module: address

Class representing an Ethereum Address with instantiation helpers and validation methods.

// ./examples/address.ts

import { Address } from '@ethereumjs/util'

const address = Address.fromString('0x2f015c60e0be116b1f0cd534704db9c92118fb6a')
console.log(`Ethereum address ${address.toString()} created`)

Module: blobs

Module providing helpers for 4844 blobs and versioned hashes.

// ./examples/blobs.ts

import { bytesToHex, computeVersionedHash, getBlobs } from '@ethereumjs/util'

const blobs = getBlobs('test input')

console.log('Created the following blobs:')

const commitment = new Uint8Array([1, 2, 3])
const blobCommitmentVersion = 0x01
const versionedHash = computeVersionedHash(commitment, blobCommitmentVersion)

console.log(`Versioned hash ${bytesToHex(versionedHash)} computed`)

Module: bytes

Byte-related helper and conversion functions.

// ./examples/bytes.ts

import { bytesToBigInt } from '@ethereumjs/util'

const bytesValue = new Uint8Array([97])
const bigIntValue = bytesToBigInt(bytesValue)

console.log(`Converted value: ${bigIntValue}`)

Module: constants

Exposed constants (e.g. KECCAK256_NULL_S for string representation of Keccak-256 hash of null)

// ./examples/constants.ts

import { BIGINT_2EXP96, KECCAK256_NULL_S } from '@ethereumjs/util'

console.log(`The keccak-256 hash of null: ${KECCAK256_NULL_S}`)
console.log(`BigInt constants (performance), e.g. BIGINT_2EXP96: ${BIGINT_2EXP96}`)

Module: db

DB interface for database abstraction (Blockchain, Trie), see e.g. @ethereumjs/trie recipes) for usage.

Module: genesis

Genesis related interfaces and helpers.

Module: internal

Internalized simple helper methods like isHexPrefixed. Note that methods from this module might get deprectared in the future.

Module: kzg

KZG interface (used for 4844 blob txs), see @ethereumjs/tx README for main usage instructions.

Module: mapDB

Simple map DB implementation using the DB interface (see above).

Module: signature

Functionality for signing, signature validation, conversion, recovery.

// ./examples/signature.ts

import { bytesToHex, ecrecover, hexToBytes } from '@ethereumjs/util'

const chainId = BigInt(3) // Ropsten

const echash = hexToBytes('0x82ff40c0a986c6a5cfad4ddf4c3aa6996f1a7837f9c398e17e5de5cbd5a12b28')
const r = hexToBytes('0x99e71a99cb2270b8cac5254f9e99b6210c6c10224a1579cf389ef88b20a1abe9')
const s = hexToBytes('0x129ff05af364204442bdb53ab6f18a99ab48acc9326fa689f228040429e3ca66')
const v = BigInt(41)

const pubkey = ecrecover(echash, v, r, s, chainId)

console.log(`Recovered public key ${bytesToHex(pubkey)} from valid signature values`)

Module: types

Various TypeScript types. Direct usage is not recommended, type structure might change in the future.

Module: withdrawal

Class representing an EIP-4895 Withdrawal with different constructors as well as conversion and output helpers.

// ./examples/withdrawal.ts

import { Withdrawal } from '@ethereumjs/util'

const withdrawal = Withdrawal.fromWithdrawalData({
  index: 0n,
  validatorIndex: 65535n,
  address: '0x0000000000000000000000000000000000000000',
  amount: 0n,

console.log('Withdrawal object created:')


With the breaking release round in Summer 2023 we have added hybrid ESM/CJS builds for all our libraries (see section below) and have eliminated many of the caveats which had previously prevented a frictionless browser usage.

It is now easily possible to run a browser build of one of the EthereumJS libraries within a modern browser using the provided ESM build. For a setup example see ./examples/browser.html.



Read the API docs.

Upgrade Helpers in bytes-Module

Depending on the extend of Buffer usage within your own libraries and other planning considerations, there are the two upgrade options to do the switch to Uint8Array yourself or keep Buffer and do transitions for input and output values.

We have updated the @ethereumjs/util bytes module with helpers for the most common conversions:

Buffer.alloc(97) // Allocate a Buffer with length 97
new Uint8Array(97) // Allocate a Uint8Array with length 97

Buffer.from('342770c0', 'hex') // Convert a hex string to a Buffer
hexToBytes('0x342770c0') // Convert a prefixed hex string to a Uint8Array, Util.hexToBytes()

`0x${myBuffer.toString('hex')}` // Convert a Buffer to a prefixed hex string
bytesToHex(myUint8Array) // Convert a Uint8Array to a prefixed hex string

intToBuffer(9) // Convert an integer to a Buffer, old (removed)
intToBytes(9) // Convert an integer to a Uint8Array, Util.intToBytes()
bytesToInt(myUint8Array) // Convert a Uint8Array to an integer, Util.bytesToInt()

bigIntToBytes(myBigInt) // Convert a BigInt to a Uint8Array, Util.bigIntToBytes()
bytesToBigInt(myUint8Array) // Convert a Uint8Array to a BigInt, Util.bytesToInt()

utf8ToBytes(myUtf8String) // Converts a UTF-8 string to a Uint8Array, Util.utf8ToBytes()
bytesToUtf8(myUint8Array) // Converts a Uint8Array to a UTF-8 string, Util.bytesToUtf8()

toBuffer(v: ToBufferInputTypes) // Converts various byte compatible types to Buffer, old (removed)
toBytes(v: ToBytesInputTypes) // Converts various byte compatible types to Uint8Array, Util.toBytes()

Helper methods can be imported like this:

import { hexToBytes } from '@ethereumjs/util'

Hybrid CJS/ESM Builds

With the breaking releases from Summer 2023 we have started to ship our libraries with both CommonJS (cjs folder) and ESM builds (esm folder), see package.json for the detailed setup.

If you use an ES6-style import in your code files from the ESM build will be used:

import { EthereumJSClass } from '@ethereumjs/[PACKAGE_NAME]'

If you use Node.js specific require, the CJS build will be used:

const { EthereumJSClass } = require('@ethereumjs/[PACKAGE_NAME]')

Using ESM will give you additional advantages over CJS beyond browser usage like static code analysis / Tree Shaking which CJS can not provide.

Buffer -> Uint8Array

With the breaking releases from Summer 2023 we have removed all Node.js specific Buffer usages from our libraries and replace these with Uint8Array representations, which are available both in Node.js and the browser (Buffer is a subclass of Uint8Array).

We have converted existing Buffer conversion methods to Uint8Array conversion methods in the @ethereumjs/util bytes module, see the respective README section for guidance.

BigInt Support

Starting with Util v8 the usage of BN.js for big numbers has been removed from the library and replaced with the usage of the native JS BigInt data type (introduced in ES2020).

Please note that number-related API signatures have changed along with this version update and the minimal build target has been updated to ES2020.

ethjs-util methods

The following methods are available by an internalized version of the ethjs-util package (MIT license), see internal.ts. The original package is not maintained any more and the original functionality will be replaced by own implementations over time (starting with the v7.1.3 release, October 2021).

  • arrayContainsArray
  • getBinarySize
  • stripHexPrefix
  • isHexPrefixed
  • isHexString
  • padToEven
  • fromAscii
  • fromUtf8
  • toUtf8
  • toAscii
  • getKeys

They can be imported by name:

import { stripHexPrefix } from '@ethereumjs/util'


See our organizational documentation for an introduction to EthereumJS as well as information on current standards and best practices. If you want to join for work or carry out improvements on the libraries, please review our contribution guidelines first.



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