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Resources common to all Ethereum implementations

Succeeds the old ethereum/common library.


npm install ethereumjs-common


All parameters can be accessed through the Common class which can be required through the main package and instantiated either with just the chain (e.g. 'mainnet') or the chain together with a specific hardfork provided.

Here are some simple usage examples:

const Common = require('ethereumjs-common')

// Instantiate with only the chain
let c = new Common('ropsten')
c.param('gasPrices', 'ecAddGas', 'byzantium') // 500

// Chain and hardfork provided
c = new Common('ropsten', 'byzantium')
c.param('pow', 'minerReward') // 3000000000000000000

// Access genesis data for Ropsten network
c.genesis().hash // 0x41941023680923e0fe4d74a34bdac8141f2540e3ae90623718e47d66d1ca4a2d

// Get bootstrap nodes for chain/network
c.bootstrapNodes() // Array with current nodes

It is encouraged to also explicitly set the supportedHardforks if the initializing library only supports a certain range of hardforks:

let c = new Common('ropsten', null, ['byzantium', 'constantinople', 'petersburg'])

This will e.g. throw an error when a param is requested for an unsupported hardfork and like this prevents unpredicted behaviour.


See the API documentation for a full list of functions for accessing specific chain and depending hardfork parameters. There are also additional helper functions like paramByBlock (topic, name, blockNumber) or hardforkIsActiveOnBlock (hardfork, blockNumber) to ease blockNumber based access to parameters.

  • API Docs

Hardfork Params

Active Hardforks

There are currently parameter changes by the following past and future hardfork by the library supported:

  • chainstart
  • homestead
  • dao
  • tangerineWhistle
  • spuriousDragon
  • byzantium
  • constantinople
  • petersburg (aka constantinopleFix, apply together with constantinople)
  • istanbul
  • muirGlacier

Future Hardforks

The muirGlacier HF delaying the difficulty bomb and scheduled for January 2020 is supported by the library since v1.5.0.

Parameter Access

For hardfork-specific parameter access with the param() and paramByBlock() functions you can use the following topics:

  • gasConfig
  • gasPrices
  • vm
  • pow
  • casper
  • sharding

See one of the hardfork files like byzantium.json in the hardforks directory for an overview. For consistency, the chain start (chainstart) is considered an own hardfork.

The hardfork-specific json files only contain the deltas from chainstart and shouldn't be accessed directly until you have a specific reason for it.

Note: The list of gasPrices and gas price changes on hardforks is consistent but not complete, so there are currently gas price values missing (PRs welcome!).

Chain Params

Supported chains:

  • mainnet
  • ropsten
  • rinkeby
  • kovan
  • goerli (final configuration since v1.1.0)
  • Private/custom chain parameters

The following chain-specific parameters are provided:

  • name
  • chainId
  • networkId
  • genesis block header values
  • hardforks block numbers
  • bootstrapNodes list

To get an overview of the different parameters have a look at one of the chain-specifc files like mainnet.json in the chains directory, or to the Chain type in ./src/types.ts.

Working with private/custom chains

There are two ways to set up a common instance with parameters for a private/custom chain:

  1. You can pass a dictionary - conforming to the parameter format described above - with your custom values in the constructor or the setChain() method for the chain parameter.

  2. You can base your custom chain's config in a standard one, using the Common.forCustomChain method.

Bootstrap Nodes

There is no separate config file for bootstrap nodes like in the old ethereum-common library. Instead use the common.bootstrapNodes() function to get nodes for a specific chain/network.

Genesis States

Network-specific genesis files are located in the genesisStates folder.

Due to the large file sizes genesis states are not directly included in the index.js file but have to be accessed directly, e.g.:

const mainnetGenesisState = require('ethereumjs-common/dist/genesisStates/mainnet')

Or by accessing dynamically:

const genesisStates = require('ethereumjs-common/dist/genesisStates')
const mainnetGenesisState = genesisStates.genesisStateByName('mainnet')
const mainnetGenesisState = genesisStates.genesisStateById(1) // alternative via network Id


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 do improvements on the libraries have a look at our contribution guidelines.



EthereumJS Common

Project is in active development and has been moved to the EthereumJS VM monorepo.

EthereumJS Common Info

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