eth_chainId - Bittensor

Example code for the eth_chainId JSON-RPC method. Complete guide on how to use eth_chainId JSON-RPC in GetBlock Web3 documentation.

Returns the EVM chain ID used for EIP-155 transaction signing. For Bittensor Subtensor EVM mainnet this is 0x3b1 (945 decimal — UTF-8 for "Alpha"). Required for correctly signing transactions.

Subtensor EVM JSON-RPC method. Call against a GetBlock endpoint configured for the EVM interface (not the Substrate interface). Subtensor EVM uses chain ID 945 (0x3b1). Standard Ethereum tooling — ethers.js, viem, Hardhat, Foundry, MetaMask — works unmodified.

Parameters

• None

Request Example

cURL

curl --location --request POST 'https://go.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "eth_chainId",
    "params": [],
    "id": "getblock.io"
}'

JavaScript (Axios)

import axios from 'axios';

const data = JSON.stringify({
    "jsonrpc": "2.0",
    "method": "eth_chainId",
    "params": [],
    "id": "getblock.io"
});

const config = {
    method: 'post',
    url: 'https://go.getblock.io/<ACCESS-TOKEN>/',
    headers: {
        'Content-Type': 'application/json'
    },
    data: data
};

axios(config)
    .then(response => console.log(JSON.stringify(response.data, null, 2)))
    .catch(error => console.log(error));

Python (Requests)

import requests
import json

url = "https://go.getblock.io/<ACCESS-TOKEN>/"

payload = json.dumps({
    "jsonrpc": "2.0",
    "method": "eth_chainId",
    "params": [],
    "id": "getblock.io"
})

headers = {
    'Content-Type': 'application/json'
}

response = requests.post(url, headers=headers, data=payload)
print(response.text)

Rust (Reqwest)

use reqwest::Client;
use serde_json::json;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = Client::new();

    let payload = json!({
        "jsonrpc": "2.0",
        "method": "eth_chainId",
        "params": [],
        "id": "getblock.io"
});

    let response = client
        .post("https://go.getblock.io/<ACCESS-TOKEN>/")
        .header("Content-Type", "application/json")
        .json(&payload)
        .send()
        .await?;

    let result: serde_json::Value = response.json().await?;
    println!("{:#?}", result);

    Ok(())
}

Response Example

{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": "0x3b1"
}

Response Parameters

Field	Type	Description
result	QUANTITY	Chain ID in hex — 0x3b1 (945) for Bittensor mainnet

Use Cases

• Mandatory before signing EVM transactions (EIP-155 replay protection)

• Detecting accidental connection to wrong network in MetaMask

Error Handling

Status Code	Error Message	Cause
403	Forbidden	Missing or invalid <ACCESS-TOKEN>
-32602	Invalid params	Request parameters are missing or malformed
-32601	Method not found	Method does not exist on this interface — check whether you're calling a Substrate method on an EVM endpoint or vice versa
-32603	Internal error	Server-side error while processing the request
429	Too Many Requests	Rate limit exceeded for your plan

SDK Integration

ethers.js

import { ethers } from 'ethers';

const provider = new ethers.JsonRpcProvider('https://go.getblock.io/<ACCESS-TOKEN>/');

// Generic JSON-RPC call (works for any EVM method):
const result = await provider.send('eth_chainId', []);
console.log(result);

// Most standard methods have typed wrappers:
// provider.getBalance(addr), provider.getBlock(n), provider.getCode(addr), etc.

viem

import { createPublicClient, http } from 'viem';

const client = createPublicClient({
    transport: http('https://go.getblock.io/<ACCESS-TOKEN>/')
});

const result = await client.request({
    method: 'eth_chainId',
    params: []
});
console.log(result);