Chain Specification - Wiki OpenEthereum Documentation

By default, when simply running openethereum, OpenEthereum will connect to the official public Ethereum network.

In order to run a chain different to the official public Ethereum one, OpenEthereum has to run with the --chain option or with a config file specifying chain = "path" under [parity]. There are a few named presets that can be selected from or a custom JSON spec file can be supplied.

Chain presets available

Private chains

OpenEthereum supports private chain and private network configuration via Chain specification file provided with --chain. In addition to the usual Proof of Work Chains, OpenEthereum also includes Proof of Authority Chains which do not require mining. More details on the available options can be found on the Pluggable Consensus page.

JSON chain spec format

A JSON file which specifies rules of a blockchain, some fields are optional which are described following the minimal example, these default to 0.

	"name": "CHAIN_NAME",
	"engine": {
			"params": {
	"genesis": {
		"seal": {
		"difficulty": "0x20000",
		"gasLimit": "0x2fefd8"
	"params": {
			"networkID" : "0x2",
			"maximumExtraDataSize": "0x20",
			"minGasLimit": "0x1388"
	"accounts": {

Optional spec fields: