chain_getHeader - Bittensor

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

Returns the block header (without the body of extrinsics) for a given block hash. Lighter than chain_getBlock when only header data is needed.

Substrate native JSON-RPC method. Call against a GetBlock endpoint configured for the Substrate interface. For typed SDK access, use Polkadot.js (TypeScript) or substrateinterface (Python).

Parameters

Parameter	Type	Required	Description
blockHash	string	No	Hex-encoded block hash. Omit for the latest block.

Request Example

cURL

curl --location --request POST 'https://go.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "chain_getHeader",
    "params": [
        "0xc0a6cfca5d4f9e1cb8a5c4b3d2e7a9c4f1b8e6d5c3a2b1f9e8d7c6b5a4f3e2d1c"
    ],
    "id": "getblock.io"
}'

JavaScript (Axios)

import axios from 'axios';

const data = JSON.stringify({
    "jsonrpc": "2.0",
    "method": "chain_getHeader",
    "params": [
        "0xc0a6cfca5d4f9e1cb8a5c4b3d2e7a9c4f1b8e6d5c3a2b1f9e8d7c6b5a4f3e2d1c"
    ],
    "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": "chain_getHeader",
    "params": [
        "0xc0a6cfca5d4f9e1cb8a5c4b3d2e7a9c4f1b8e6d5c3a2b1f9e8d7c6b5a4f3e2d1c"
    ],
    "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": "chain_getHeader",
        "params": [
                "0xc0a6cfca5d4f9e1cb8a5c4b3d2e7a9c4f1b8e6d5c3a2b1f9e8d7c6b5a4f3e2d1c"
        ],
        "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": {
        "parentHash": "0x47edbdc8da5cd1b3127ea8f1ce5da6739fa39e7e6d2eb1c9b50f1c83de0a98b4",
        "number": "0x599f5a",
        "stateRoot": "0x123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0",
        "extrinsicsRoot": "0xfedcba9876543210fedcba9876543210fedcba9876543210fedcba9876543210",
        "digest": {
            "logs": [
                "0x0642424542340183e9..."
            ]
        }
    }
}

Response Parameters

Field	Type	Description
result.parentHash	string	Parent block hash
result.number	string	Block number in hex
result.stateRoot	string	State trie root hash
result.extrinsicsRoot	string	Extrinsics trie root hash
result.digest	object	Block digest — consensus engine logs, seal, etc.

Use Cases

• Lightweight block scanning (faster than fetching full blocks)

• Header-chain verification in light clients

• Real-time block notifications with minimal data transfer

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

Polkadot.js (TypeScript)

import { ApiPromise, WsProvider } from '@polkadot/api';

const provider = new WsProvider('wss://go.getblock.io/<ACCESS-TOKEN>/');
const api = await ApiPromise.create({ provider });

// Typed wrapper: api.rpc.chain.getHeader(...)
const result = await api.rpc.chain.getHeader("0xc0a6cfca5d4f9e1cb8a5c4b3d2e7a9c4f1b8e6d5c3a2b1f9e8d7c6b5a4f3e2d1c");
console.log(result.toHuman());

// Or use the raw RPC interface for any method:
// const raw = await api.rpc.send({ method: 'chain_getHeader', params: ["0xc0a6cfca5d4f9e1cb8a5c4b3d2e7a9c4f1b8e6d5c3a2b1f9e8d7c6b5a4f3e2d1c"] });

substrateinterface (Python)

from substrateinterface import SubstrateInterface

substrate = SubstrateInterface(url="wss://go.getblock.io/<ACCESS-TOKEN>/")

# Generic RPC call:
result = substrate.rpc_request("chain_getHeader", ["0xc0a6cfca5d4f9e1cb8a5c4b3d2e7a9c4f1b8e6d5c3a2b1f9e8d7c6b5a4f3e2d1c"])
print(result)