eth_chainId

Returns the chain ID of the currently connected network. The chain ID is used to prevent replay attacks across different networks.

Parameters

None

Returns

string - The chain ID as a hexadecimal string

Example


const chainId = await window.$onekey.ethereum.request({
  method: 'eth_chainId'
})
 
console.log('Chain ID (hex):', chainId)
console.log('Chain ID (decimal):', parseInt(chainId, 16))

Check Network


const CHAIN_IDS = {
  ETHEREUM: '0x1',
  POLYGON: '0x89',
  BSC: '0x38',
  ARBITRUM: '0xa4b1',
  OPTIMISM: '0xa',
  BASE: '0x2105'
}
 
async function checkNetwork() {
  const chainId = await window.$onekey.ethereum.request({
    method: 'eth_chainId'
  })
 
  switch (chainId) {
    case CHAIN_IDS.ETHEREUM:
      console.log('Connected to Ethereum Mainnet')
      break
    case CHAIN_IDS.POLYGON:
      console.log('Connected to Polygon')
      break
    default:
      console.log('Connected to chain:', parseInt(chainId, 16))
  }
 
  return chainId
}

Require Specific Network


async function requireNetwork(requiredChainId) {
  const chainId = await window.$onekey.ethereum.request({
    method: 'eth_chainId'
  })
 
  if (chainId !== requiredChainId) {
    try {
      await window.$onekey.ethereum.request({
        method: 'wallet_switchEthereumChain',
        params: [{ chainId: requiredChainId }]
      })
    } catch (error) {
      if (error.code === 4902) {
        throw new Error('Please add this network to your wallet')
      }
      throw error
    }
  }
}
 
// Usage
await requireNetwork('0x1') // Require Ethereum Mainnet

Common Chain IDs

Network	Hex	Decimal
Ethereum Mainnet	`0x1`	1
Goerli Testnet	`0x5`	5
Sepolia Testnet	`0xaa36a7`	11155111
Polygon	`0x89`	137
BSC	`0x38`	56
Arbitrum One	`0xa4b1`	42161
Optimism	`0xa`	10
Base	`0x2105`	8453
Avalanche C-Chain	`0xa86a`	43114

Errors

Code	Message	Description
-32603	Internal error	Provider error

Notes

The chain ID is always returned as a hex string with 0x prefix
Listen to chainChanged event to detect network changes
Specified by EIP-695


window.$onekey.ethereum.on('chainChanged', (chainId) => {
  console.log('Network changed to:', chainId)
  // Recommended: reload the page
  window.location.reload()
})