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Implements schema and functions related to Ethereum's block.

Note: this README reflects the state of the library from v3.0.0 onwards. See README from the standalone repository for an introduction on the last preceding release.


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

npm install @ethereumjs/block

Note: If you want to work with EIP-4844 related functionality, you will have additional manual installation steps for the KZG setup, see related section below.



There are five static factories to instantiate a Block:

  • Block.fromBlockData(blockData: BlockData = {}, opts?: BlockOptions)
  • Block.fromRLPSerializedBlock(serialized: Uint8Array, opts?: BlockOptions)
  • Block.fromValuesArray(values: BlockBytes, opts?: BlockOptions)
  • Block.fromRPC(blockData: JsonRpcBlock, uncles?: any[], opts?: BlockOptions)
  • Block.fromJsonRpcProvider(provider: string | EthersProvider, blockTag: string | bigint, opts: BlockOptions)

For BlockHeader instantiation analog factory methods exists, see API docs linked below.

Instantiation Example:

// ./examples/simple.ts

import { BlockHeader } from '@ethereumjs/block'
import { bytesToHex } from '@ethereumjs/util'

const headerData = {
  number: 15,
  parentHash: '0x6bfee7294bf44572b7266358e627f3c35105e1c3851f3de09e6d646f955725a7',
  gasLimit: 8000000,
  timestamp: 1562422144,
const header = BlockHeader.fromHeaderData(headerData)
console.log(`Created block header with hash=${bytesToHex(header.hash())}`)

Properties of a Block or BlockHeader object are frozen with Object.freeze() which gives you enhanced security and consistency properties when working with the instantiated object. This behavior can be modified using the freeze option in the constructor if needed.

API Usage Example:

try {
  await block.validateData()
  // Block data validation has passed
} catch (err) {
  // handle errors appropriately

EIP-1559 Blocks

This library supports the creation of EIP-1559 compatible blocks starting with v3.3.0. For this to work a Block needs to be instantiated with a Hardfork greater or equal to London (Hardfork.London).

// ./examples/1559.ts

import { Block } from '@ethereumjs/block'
import { Chain, Common, Hardfork } from '@ethereumjs/common'
const common = new Common({ chain: Chain.Mainnet, hardfork: Hardfork.London })

const block = Block.fromBlockData(
    header: {
      baseFeePerGas: BigInt(10),
      gasLimit: BigInt(100),
      gasUsed: BigInt(60),
  { common }

// Base fee will increase for next block since the
// gas used is greater than half the gas limit
console.log(Number(block.header.calcNextBaseFee())) // 11

// So for creating a block with a matching base fee in a certain
// chain context you can do:
const blockWithMatchingBaseFee = Block.fromBlockData(
    header: {
      baseFeePerGas: block.header.calcNextBaseFee(),
      gasLimit: BigInt(100),
      gasUsed: BigInt(60),
  { common }

console.log(Number(blockWithMatchingBaseFee.header.baseFeePerGas)) // 11

EIP-1559 blocks have an extra baseFeePerGas field (default: BigInt(7)) and can encompass FeeMarketEIP1559Transaction txs (type 2) (supported by @ethereumjs/tx v3.2.0 or higher) as well as LegacyTransaction legacy txs (internal type 0) and AccessListEIP2930Transaction txs (type 1).

EIP-4895 Beacon Chain Withdrawals Blocks

Starting with the v4.1.0 release there is support for EIP-4895 beacon chain withdrawals. Withdrawals support can be activated by initializing a Common object with a hardfork set to shanghai (default) or higher and then use the withdrawals data option to pass in system-level withdrawal operations together with a matching withdrawalsRoot (mandatory when EIP-4895 is activated) along Block creation, see the following example:

// ./examples/withdrawals.ts

import { Block } from '@ethereumjs/block'
import { Common, Chain } from '@ethereumjs/common'
import { Address, hexToBytes } from '@ethereumjs/util'
import type { WithdrawalData } from '@ethereumjs/util'

const common = new Common({ chain: Chain.Mainnet })

const withdrawal = <WithdrawalData>{
  index: BigInt(0),
  validatorIndex: BigInt(0),
  address: new Address(hexToBytes(`0x${'20'.repeat(20)}`)),
  amount: BigInt(1000),

const block = Block.fromBlockData(
    header: {
      withdrawalsRoot: hexToBytes(
    withdrawals: [withdrawal],

console.log(`Block with ${block.withdrawals!.length} withdrawal(s) created`)

Validation of the withdrawals trie can be manually triggered with the newly introduced async Block.withdrawalsTrieIsValid() method.

EIP-4844 Shard Blob Transaction Blocks

This library supports the blob transaction type introduced with EIP-4844 as being specified in the b9a5a11 EIP version from July 2023 deployed along 4844-devnet-7 (July 2023), see PR #2349 and following.

Note: 4844 support is not yet completely stable and there will still be (4844-)breaking changes along all types of library releases.


To create blocks which include blob transactions you have to active EIP-4844 in the associated @ethereumjs/common library or use a 4844-including hardfork like Cancun:

// ./examples/4844.ts

import { Common, Chain, Hardfork } from '@ethereumjs/common'
import { BlockHeader } from '@ethereumjs/block'

const common = new Common({ chain: Chain.Mainnet, hardfork: Hardfork.Cancun })

// TODO: add a more meaningful example including at least one blob tx
const header = BlockHeader.fromHeaderData(
    excessBlobGas: 0n,
    skipConsensusFormatValidation: true,

console.log(`4844 block header with excessBlobGas=${header.excessBlobGas} created`)

Note: Working with blob transactions needs a manual KZG library installation and global initialization, see KZG Setup for instructions.

Consensus Types

The block library supports the creation as well as consensus format validation of PoW ethash and PoA clique blocks (so e.g. do specific extraData checks on Clique/PoA blocks).

Consensus format validation logic is encapsulated in the semi-private BlockHeader._consensusFormatValidation() method called from the constructor. If you want to add your own validation logic you can overwrite this method with your own rules.

Note: Starting with v4 consensus validation itself (e.g. Ethash verification) has moved to the Blockchain package.


An Ethash/PoW block can be instantiated as follows:

// ./examples/pow.ts

import { Block } from '@ethereumjs/block'
import { Chain, Common, Hardfork } from '@ethereumjs/common'

const common = new Common({ chain: Chain.Mainnet, hardfork: Hardfork.Chainstart })

console.log(common.consensusType()) // 'pow'
console.log(common.consensusAlgorithm()) // 'ethash'

Block.fromBlockData({}, { common })
console.log(`Old Proof-of-Work block created`)

To calculate the difficulty when creating the block pass in the block option calcDifficultyFromHeader with the preceding (parent) BlockHeader.

Clique/PoA (since v3.1.0)

A clique block can be instantiated as follows:

// ./examples/clique.ts

import { Block } from '@ethereumjs/block'
import { Chain, Common, Hardfork } from '@ethereumjs/common'

const common = new Common({ chain: Chain.Goerli, hardfork: Hardfork.Chainstart })

console.log(common.consensusType()) // 'poa'
console.log(common.consensusAlgorithm()) // 'clique'

Block.fromBlockData({ header: { extraData: new Uint8Array(97) } }, { common })
console.log(`Old Clique Proof-of-Authority block created`)

For sealing a block on instantiation you can use the cliqueSigner constructor option:

const cliqueSigner = Buffer.from('PRIVATE_KEY_HEX_STRING', 'hex')
const block = Block.fromHeaderData(headerData, { cliqueSigner })

Additionally there are the following utility methods for Clique/PoA related functionality in the BlockHeader class:

  • BlockHeader.cliqueSigHash()
  • BlockHeader.cliqueIsEpochTransition(): boolean
  • BlockHeader.cliqueExtraVanity(): Uint8Array
  • BlockHeader.cliqueExtraSeal(): Uint8Array
  • BlockHeader.cliqueEpochTransitionSigners(): Address[]
  • BlockHeader.cliqueVerifySignature(signerList: Address[]): boolean
  • BlockHeader.cliqueSigner(): Address

See the API docs for detailed documentation. Note that these methods will throw if called in a non-Clique/PoA context.

Casper/PoS (since v3.5.0)

Merge-friendly Casper/PoS blocks have been introduced along with the v3.5.0 release. Proof-of-Stake compatible execution blocks come with their own set of header field simplifications and associated validation rules. The difficulty is set to 0 since not relevant anymore, just to name an example. For a full list of changes see EIP-3675.

You can instantiate a Merge/PoS block like this:

// ./examples/pos.ts

import { Block } from '@ethereumjs/block'
import { Chain, Common } from '@ethereumjs/common'

const common = new Common({ chain: Chain.Mainnet })

const block = Block.fromBlockData(
    // Provide your block data here or use default values
  { common }

console.log(`Proof-of-Stake (default) block created with hardfork=${block.common.hardfork()}`)


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.



Generated TypeDoc API Documentation

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 v4 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.


Tests in the tests directory are partly outdated and testing is primarily done by running the BlockchainTests from within the @ethereumjs/vm package.

To avoid bloating this repository with ethereum/tests JSON files, we usually copy specific JSON files and wrap them with some metadata (source, date, commit hash). There's a helper to aid in that process and can be found at wrap-ethereum-test.sh.


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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