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chain_getBlockHash

Description​

Retrieves the block hash for a specific block number. When called without parameters, returns the hash of the latest block. This method is commonly used to get block identifiers for historical queries.

Parameters​

ParameterTypeRequiredDescription
blockNumbernumberNoBlock number to get hash for. If omitted, returns latest block hash

Returns​

FieldTypeDescription
resultstringHex-encoded block hash

Request Example​

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

Response Example​

{
  "jsonrpc": "2.0",
  "result": "0x5d83e66b61701da7b6e3e8c9d8e2e57e1391e3e58e677b30e1f391d568c9ca24",
  "id": 1
}

Code Examples​

JavaScript​

const getBlockHash = async (blockNumber = null) => {
  const params = blockNumber !== null ? [blockNumber] : [];
  
  const response = await fetch('https://api-polkadot.n.dwellir.com', {
    method: 'POST',
    headers: {
      'Authorization': 'Bearer YOUR_API_KEY',
      'Content-Type': 'application/json'
    },
    body: JSON.stringify({
      jsonrpc: '2.0',
      method: 'chain_getBlockHash',
      params: params,
      id: 1
    })
  });
  
  const data = await response.json();
  return data.result;
};

// Get latest block hash
const latestHash = await getBlockHash();
console.log('Latest block hash:', latestHash);

// Get specific block hash
const historicalHash = await getBlockHash(1000000);
console.log('Block 1000000 hash:', historicalHash);

Python​

import requests
import json

def get_block_hash(block_number=None):
    url = "https://api-polkadot.n.dwellir.com"
    headers = {
        "Authorization": "Bearer YOUR_API_KEY",
        "Content-Type": "application/json"
    }
    
    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, headers=headers, data=json.dumps(payload))
    return response.json()["result"]

# Get genesis block hash
genesis_hash = get_block_hash(0)
print(f"Genesis block: {genesis_hash}")