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": []
}
'import requests
url = "https://monad-testnet.core.chainstack.com/9c5b265f20b3ea5df4f54f70eb74b800/"
payload = {
"id": 1,
"jsonrpc": "2.0",
"method": "eth_chainId",
"params": []
}
headers = {"Content-Type": "application/json"}
response = requests.post(url, json=payload, headers=headers)
print(response.text)const options = {
method: 'POST',
headers: {'Content-Type': 'application/json'},
body: JSON.stringify({id: 1, jsonrpc: '2.0', method: 'eth_chainId', params: []})
};
fetch('https://monad-testnet.core.chainstack.com/9c5b265f20b3ea5df4f54f70eb74b800/', options)
.then(res => res.json())
.then(res => console.log(res))
.catch(err => console.error(err));<?php
$curl = curl_init();
curl_setopt_array($curl, [
CURLOPT_URL => "https://monad-testnet.core.chainstack.com/9c5b265f20b3ea5df4f54f70eb74b800/",
CURLOPT_RETURNTRANSFER => true,
CURLOPT_ENCODING => "",
CURLOPT_MAXREDIRS => 10,
CURLOPT_TIMEOUT => 30,
CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
CURLOPT_CUSTOMREQUEST => "POST",
CURLOPT_POSTFIELDS => json_encode([
'id' => 1,
'jsonrpc' => '2.0',
'method' => 'eth_chainId',
'params' => [
]
]),
CURLOPT_HTTPHEADER => [
"Content-Type: application/json"
],
]);
$response = curl_exec($curl);
$err = curl_error($curl);
curl_close($curl);
if ($err) {
echo "cURL Error #:" . $err;
} else {
echo $response;
}package main
import (
"fmt"
"strings"
"net/http"
"io"
)
func main() {
url := "https://monad-testnet.core.chainstack.com/9c5b265f20b3ea5df4f54f70eb74b800/"
payload := strings.NewReader("{\n \"id\": 1,\n \"jsonrpc\": \"2.0\",\n \"method\": \"eth_chainId\",\n \"params\": []\n}")
req, _ := http.NewRequest("POST", url, payload)
req.Header.Add("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)
defer res.Body.Close()
body, _ := io.ReadAll(res.Body)
fmt.Println(string(body))
}HttpResponse<String> response = Unirest.post("https://monad-testnet.core.chainstack.com/9c5b265f20b3ea5df4f54f70eb74b800/")
.header("Content-Type", "application/json")
.body("{\n \"id\": 1,\n \"jsonrpc\": \"2.0\",\n \"method\": \"eth_chainId\",\n \"params\": []\n}")
.asString();require 'uri'
require 'net/http'
url = URI("https://monad-testnet.core.chainstack.com/9c5b265f20b3ea5df4f54f70eb74b800/")
http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true
request = Net::HTTP::Post.new(url)
request["Content-Type"] = 'application/json'
request.body = "{\n \"id\": 1,\n \"jsonrpc\": \"2.0\",\n \"method\": \"eth_chainId\",\n \"params\": []\n}"
response = http.request(request)
puts response.read_body{
"jsonrpc": "<string>",
"id": 123,
"result": "<string>"
}Monad node API
eth_chainId | Monad
Monad API method that returns the chain ID of the current network. eth_chainId JSON-RPC method available on the Monad blockchain via Chainstack.
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": []
}
'import requests
url = "https://monad-testnet.core.chainstack.com/9c5b265f20b3ea5df4f54f70eb74b800/"
payload = {
"id": 1,
"jsonrpc": "2.0",
"method": "eth_chainId",
"params": []
}
headers = {"Content-Type": "application/json"}
response = requests.post(url, json=payload, headers=headers)
print(response.text)const options = {
method: 'POST',
headers: {'Content-Type': 'application/json'},
body: JSON.stringify({id: 1, jsonrpc: '2.0', method: 'eth_chainId', params: []})
};
fetch('https://monad-testnet.core.chainstack.com/9c5b265f20b3ea5df4f54f70eb74b800/', options)
.then(res => res.json())
.then(res => console.log(res))
.catch(err => console.error(err));<?php
$curl = curl_init();
curl_setopt_array($curl, [
CURLOPT_URL => "https://monad-testnet.core.chainstack.com/9c5b265f20b3ea5df4f54f70eb74b800/",
CURLOPT_RETURNTRANSFER => true,
CURLOPT_ENCODING => "",
CURLOPT_MAXREDIRS => 10,
CURLOPT_TIMEOUT => 30,
CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
CURLOPT_CUSTOMREQUEST => "POST",
CURLOPT_POSTFIELDS => json_encode([
'id' => 1,
'jsonrpc' => '2.0',
'method' => 'eth_chainId',
'params' => [
]
]),
CURLOPT_HTTPHEADER => [
"Content-Type: application/json"
],
]);
$response = curl_exec($curl);
$err = curl_error($curl);
curl_close($curl);
if ($err) {
echo "cURL Error #:" . $err;
} else {
echo $response;
}package main
import (
"fmt"
"strings"
"net/http"
"io"
)
func main() {
url := "https://monad-testnet.core.chainstack.com/9c5b265f20b3ea5df4f54f70eb74b800/"
payload := strings.NewReader("{\n \"id\": 1,\n \"jsonrpc\": \"2.0\",\n \"method\": \"eth_chainId\",\n \"params\": []\n}")
req, _ := http.NewRequest("POST", url, payload)
req.Header.Add("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)
defer res.Body.Close()
body, _ := io.ReadAll(res.Body)
fmt.Println(string(body))
}HttpResponse<String> response = Unirest.post("https://monad-testnet.core.chainstack.com/9c5b265f20b3ea5df4f54f70eb74b800/")
.header("Content-Type", "application/json")
.body("{\n \"id\": 1,\n \"jsonrpc\": \"2.0\",\n \"method\": \"eth_chainId\",\n \"params\": []\n}")
.asString();require 'uri'
require 'net/http'
url = URI("https://monad-testnet.core.chainstack.com/9c5b265f20b3ea5df4f54f70eb74b800/")
http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true
request = Net::HTTP::Post.new(url)
request["Content-Type"] = 'application/json'
request.body = "{\n \"id\": 1,\n \"jsonrpc\": \"2.0\",\n \"method\": \"eth_chainId\",\n \"params\": []\n}"
response = http.request(request)
puts response.read_body{
"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)
- Monad Mainnet:
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();
from web3 import Web3
node_url = "CHAINSTACK_NODE_URL"
web3 = Web3(Web3.HTTPProvider(node_url))
chain_id = web3.eth.chain_id
print(f'Chain ID: {chain_id}')
Use case
A practical use case foreth_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.Last modified on June 22, 2026
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