chain_getBlockHash

Returns the block hash for a given block number on Kusama.

Use Cases

• Historical queries - Convert block numbers to hashes
• Block navigation - Navigate blockchain history for parachain experimentation, early feature deployment, and production-grade testing with real value
• Data indexing - Build block number to hash mappings

Parameters

Parameter	Type	Required	Description
blockNumber	Number	No	Block number. If omitted, returns latest block hash

Request

{
  "jsonrpc": "2.0",
  "method": "chain_getBlockHash",
  "params": [1000000],
  "id": 1
}

Code Examples

cURL

curl  \
  -X POST \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "chain_getBlockHash",
    "params": [1000000],
    "id": 1
  }'

JavaScript

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

const provider = new WsProvider('');
const api = await ApiPromise.create({ provider });

// Get hash for specific block number
const blockNumber = 1000000;
const blockHash = await api.rpc.chain.getBlockHash(blockNumber);
console.log(`Block ${blockNumber} hash:`, blockHash.toHex());

await api.disconnect();

Python

import requests

def get_block_hash(block_number=None):
    url = ''
    params = [block_number] if block_number is not None else []

    payload = {
        'jsonrpc': '2.0',
        'method': 'chain_getBlockHash',
        'params': params,
        'id': 1
    }

    response = requests.post(url, json=payload)
    return response.json()['result']

block_hash = get_block_hash(1000000)
print(f'Block hash: {block_hash}')

Related Methods

• chain_getBlock - Get block by hash
• chain_getHeader - Get block header