chain_getBlock - JSON-RPC Method

Description

Retrieves complete block information from the Polkadot blockchain, including the block header, extrinsics, and justifications. When called without parameters, returns the latest block.

Parameters

Parameter	Type	Required	Description
blockHash	string	No	Hex-encoded block hash. If omitted, returns the latest block

Returns

Field	Type	Description
block	object	Complete block data
block.header	object	Block header information
block.header.parentHash	string	Hash of the parent block
block.header.number	string	Block number (hex-encoded)
block.header.stateRoot	string	Root of the state trie
block.header.extrinsicsRoot	string	Root of the extrinsics trie
block.header.digest	object	Block digest items
block.extrinsics	array	Array of extrinsics in the block
justifications	array	Block justifications (if available)

Request Example

{
  "jsonrpc": "2.0",
  "method": "chain_getBlock",
  "params": [
    "0x5d83e66b61701da7b6e3e8c9d8e2e57e1391e3e58e677b30e1f391d568c9ca24"
  ],
  "id": 1
}

Response Example

{
  "jsonrpc": "2.0",
  "result": {
    "block": {
      "header": {
        "parentHash": "0x4a84d1c5fc5c725b26a3c8e126d8f65e1c2d2dc5b3fcbc91e67e7637fa136789",
        "number": "0x123456",
        "stateRoot": "0x8f7a82e2e0f3e73f5e232e68de18144f6e7a52a6db39bb5e5e3d9ca6e1f72845",
        "extrinsicsRoot": "0x2e6f9a7d2c4b3e1a8f5c6d9e4b1a7c3f8e5d2a9b6c4e1f8a5d3c2b9e7f6a4d38",
        "digest": {
          "logs": [
            "0x0642414245b501013c0000009d2ef70f00000000",
            "0x054241424501019e7b3c4e1f8a2d5c6b9e4f3a7d2c5e8b1f4a6d9c3e2b5f8a7c4d"
          ]
        }
      },
      "extrinsics": [
        "0x280402000b50cd548d8501",
        "0x450284008eaf04151687736326c9fea17e25fc5287613693c912909cb226aa4794f26a48"
      ]
    },
    "justifications": null
  },
  "id": 1
}

Code Examples

cURL

# Get latest block
curl https://api-polkadot.n.dwellir.com \
  -X POST \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "chain_getBlock",
    "params": [],
    "id": 1
  }'

# Get specific block
curl https://api-polkadot.n.dwellir.com \
  -X POST \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "chain_getBlock",
    "params": ["0x5d83e66b61701da7b6e3e8c9d8e2e57e1391e3e58e677b30e1f391d568c9ca24"],
    "id": 1
  }'

JavaScript (fetch)

const getBlock = async (blockHash = null) => {
  const params = blockHash ? [blockHash] : [];
  
  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_getBlock',
      params: params,
      id: 1
    })
  });
  
  const data = await response.json();
  return data.result;
};

// Get latest block
const latestBlock = await getBlock();
console.log('Latest block number:', parseInt(latestBlock.block.header.number, 16));

// Get specific block
const specificBlock = await getBlock('0x5d83e66b...');
console.log('Block extrinsics:', specificBlock.block.extrinsics);

Python (requests)

import requests
import json

def get_block(block_hash=None):
    url = "https://api-polkadot.n.dwellir.com"
    headers = {
        "Authorization": "Bearer YOUR_API_KEY",
        "Content-Type": "application/json"
    }
    
    params = [block_hash] if block_hash else []
    
    payload = {
        "jsonrpc": "2.0",
        "method": "chain_getBlock",
        "params": params,
        "id": 1
    }
    
    response = requests.post(url, headers=headers, data=json.dumps(payload))
    data = response.json()
    
    if "error" in data:
        raise Exception(f"RPC Error: {data['error']}")
    
    return data["result"]

# Get latest block
latest_block = get_block()
block_number = int(latest_block["block"]["header"]["number"], 16)
print(f"Latest block number: {block_number}")

# Get specific block
specific_block = get_block("0x5d83e66b...")
print(f"Extrinsics count: {len(specific_block['block']['extrinsics'])}")

TypeScript (@polkadot/api)

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

async function getBlockData() {
  const provider = new WsProvider('wss://api-polkadot.n.dwellir.com');
  const api = await ApiPromise.create({ provider });
  
  // Get latest block
  const latestHash = await api.rpc.chain.getBlockHash();
  const latestBlock = await api.rpc.chain.getBlock(latestHash);
  
  console.log('Latest block:', {
    number: latestBlock.block.header.number.toNumber(),
    hash: latestHash.toHex(),
    extrinsicsCount: latestBlock.block.extrinsics.length
  });
  
  // Get block at specific height
  const blockHash = await api.rpc.chain.getBlockHash(1000000);
  const block = await api.rpc.chain.getBlock(blockHash);
  
  // Parse extrinsics
  block.block.extrinsics.forEach((ex, index) => {
    console.log(`Extrinsic ${index}:`, ex.toHuman());
  });
  
  await api.disconnect();
}

Use Cases

1. Block Explorers: Display block details and transaction history
2. Chain Analysis: Analyze block production patterns and extrinsic distribution
3. Transaction Verification: Confirm transaction inclusion in specific blocks
4. Network Monitoring: Track block production and finalization
5. Data Indexing: Build databases of historical blockchain data

Block Structure Details

Header Fields

• parentHash: Links blocks in the chain
• number: Sequential block identifier
• stateRoot: Merkle root of all account states
• extrinsicsRoot: Merkle root of all extrinsics
• digest: Contains consensus-related data (BABE, GRANDPA)

Extrinsics

Each extrinsic in the array is hex-encoded and contains:

• Signature (for signed extrinsics)
• Method call data
• Additional parameters (nonce, tip, mortality)

Related Methods

• chain_getBlockHash - Get block hash by number
• state_getStorage - Query state at specific block
• state_getMetadata - Get runtime metadata
• system_health - Check node sync status

Notes

• Block numbers are hex-encoded in responses
• Extrinsics are returned as hex-encoded SCALE data
• Justifications are only present for finalized blocks with GRANDPA proofs
• Latest block may not be finalized - use chain_getFinalizedHead for finalized blocks
• Block data can be large - consider using chain_getHeader if only header is needed