chain_getHeader - Polkadot

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

This method returns the header of a block by its hash, without the extrinsics. If no hash is supplied, the latest block header is returned.

Parameters

Parameter	Type	Required	Description
hash	string	No	Block hash. Defaults to the latest block when omitted

Request

cURL

curl --location --request POST 'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{"jsonrpc": "2.0", "method": "chain_getHeader", "params": ["0x255bc00927df8d33d561792635cbc6bde480a0a505eef5ff28630ece3fc15b32"], "id": "getblock.io"}'

JavaScript

example.js

const response = await fetch('https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
        jsonrpc: '2.0',
        method: 'chain_getHeader',
        params: ["0x255bc00927df8d33d561792635cbc6bde480a0a505eef5ff28630ece3fc15b32"],
        id: 'getblock.io'
    })
});

const data = await response.json();
console.log(data.result);

Python

example.py

import requests

response = requests.post(
    'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/',
    headers={'Content-Type': 'application/json'},
    json={
        'jsonrpc': '2.0',
        'method': 'chain_getHeader',
        'params': ["0x255bc00927df8d33d561792635cbc6bde480a0a505eef5ff28630ece3fc15b32"],
        'id': 'getblock.io'
    }
)

print(response.json()['result'])

Response

{
    "id": "getblock.io",
    "jsonrpc": "2.0",
    "result": {
        "digest": {
            "logs": [
                "0x0642414245b5010392...",
                "0x0542414245010114a5..."
            ]
        },
        "extrinsicsRoot": "0xada254ef8321e28a6667ad75659be6464944174bd5540667da94590a0a4a596f",
        "number": "0x67103a",
        "parentHash": "0x570e3f417a41646d9b978bf2ac3d68be48bb0f73082825f438af58a37cfe0ef8",
        "stateRoot": "0x176c67eca385c24403ba774550ff75dcfa652d6d6cf2d2ecbccf56e513db601c"
    }
}

Response Parameters

Parameter	Type	Description
id	string	Request identifier matching the request
jsonrpc	string	JSON-RPC protocol version ("2.0")
result	object	Block header object

Result Object

Field	Type	Description
parentHash	string	Hash of the parent block header
number	string	Block number, hex-encoded
stateRoot	string	Root hash of the state trie after the block
extrinsicsRoot	string	Root hash of the extrinsics trie
digest	object	Consensus digest logs (BABE, GRANDPA, and others)

Use Cases

• Lightweight Sync: Read headers without downloading full blocks

• State Roots: Read the state root for proof verification

• Chain Following: Track the head by reading successive headers

• Digest Inspection: Read consensus logs from the header digest

Error Handling

Error Code	Message	Description
-32602	Invalid params	A parameter is missing or has the wrong type or format
-32601	Method not found	The method is not available on this endpoint
-32603	Internal error	The node failed to process the request

Library Integration

The idiomatic way to call Polkadot RPC is the Polkadot.js API (@polkadot/api), which connects over WebSocket and exposes the method as api.rpc.chain.getHeader.

polkadot-js.js

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

const provider = new WsProvider('wss://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/');
const api = await ApiPromise.create({ provider });

const result = await api.rpc.chain.getHeader('0x255bc00927df8d33d561792635cbc6bde480a0a505eef5ff28630ece3fc15b32');
console.log(result.toHuman());