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POST
eth_chainId
curl --request POST \
  --url https://monad-testnet.core.chainstack.com/9c5b265f20b3ea5df4f54f70eb74b800/ \
  --header 'Content-Type: application/json' \
  --data '
{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "eth_chainId",
  "params": []
}
'
{
  "jsonrpc": "<string>",
  "id": 123,
  "result": "<string>"
}
Monad API method that returns the chain ID of the current network. The chain ID is used for transaction signing to prevent replay attacks across different networks.
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​
Parameters

  • none

​
Response

  • result — the current chain ID as a hexadecimal string:
    • Monad Mainnet: 0x8f (143)
    • Monad Testnet: 0x279f (10143)

​
eth_chainId code examples

const { ethers } = require("ethers");

const provider = new ethers.JsonRpcProvider("CHAINSTACK_NODE_URL");

async function getChainId() {
  const network = await provider.getNetwork();
  console.log(`Chain ID: ${network.chainId}`);
}

getChainId();

​
Use case

A practical use case for eth_chainId is verifying that your application is connected to the correct network before sending transactions, which is essential for preventing accidental transactions on the wrong network.

Body

application/json
​
id
integer
default:1
​
jsonrpc
string
default:2.0
​
method
string
default:eth_chainId
​
params
array

Response

200 - application/json

The chain ID.

​
jsonrpc
string
​
id
integer
​
result
string
Last modified on May 18, 2026