getblockheader - Zcash

Example code for the getblockheader JSON-RPC method. Сomplete guide on how to use the getblockheader JSON-RPC method in GetBlock.io Web3 documentation.

This method returns block header data — the fixed 80-byte header plus derived fields — without the full transaction list. Significantly cheaper than getblock when only header data is needed, such as during header-first chain synchronization or SPV-style verification.

Parameters

Parameter	Type	Required	Description
blockhash	string	Yes	Block hash (hex string)
verbose	boolean	No	If true (default), returns a JSON object; if false, returns raw hex-encoded header

Request

cURL

curl --location --request POST 'https://go.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "getblockheader",
    "params": [
        "00000000018bb43cadf5b4c8a2e7f9d0e1a6b3c8d5e4f2a1b0c9d8e7f6a5b4c3",
        true
    ],
    "id": "getblock.io"
}'

Axios

example.js

const axios = require('axios');

const response = await axios.post('https://go.getblock.io/<ACCESS-TOKEN>/', {
    jsonrpc: '2.0',
    method: 'getblockheader',
    params: [
        "00000000018bb43cadf5b4c8a2e7f9d0e1a6b3c8d5e4f2a1b0c9d8e7f6a5b4c3",
        true
    ],
    id: 'getblock.io'
}, {
    headers: { 'Content-Type': 'application/json' }
});

console.log(response.data.result);

Request

example.py

import requests

response = requests.post(
    'https://go.getblock.io/<ACCESS-TOKEN>/',
    headers={'Content-Type': 'application/json'},
    json={
        'jsonrpc': '2.0',
        'method': 'getblockheader',
        'params': [
        "00000000018bb43cadf5b4c8a2e7f9d0e1a6b3c8d5e4f2a1b0c9d8e7f6a5b4c3",
        true
    ],
        'id': 'getblock.io'
    }
)

print(response.json())

Rust

example.rs

use reqwest::Client;
use serde_json::{json, Value};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = Client::new();
    
    let response = client
        .post("https://go.getblock.io/<ACCESS-TOKEN>/")
        .header("Content-Type", "application/json")
        .json(&json!({
            "jsonrpc": "2.0",
            "method": "getblockheader",
            "params": [
        "00000000018bb43cadf5b4c8a2e7f9d0e1a6b3c8d5e4f2a1b0c9d8e7f6a5b4c3",
        true
    ],
            "id": "getblock.io"
        }))
        .send()
        .await?
        .json::<Value>()
        .await?;
    
    println!("Result: {}", response["result"]);
    Ok(())
}

Response

{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": {
        "hash": "00000000018bb43cadf5b4c8a2e7f9d0e1a6b3c8d5e4f2a1b0c9d8e7f6a5b4c3",
        "confirmations": 1,
        "height": 2856342,
        "version": 4,
        "merkleroot": "3a2b1c9d8e7f6a5b4c3d2e1f0a9b8c7d6e5f4a3b2c1d0e9f8a7b6c5d4e3f2a1b",
        "blockcommitments": "5eae9c5cbe0e8d3e2f5cd8b0a4e3b1f2c9d8e7f6a5b4c3d2e1f0a9b8c7d6e5f4",
        "finalsaplingroot": "01a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f4a5b6c7d8e9f0a1",
        "time": 1747852800,
        "nonce": "0000000000000000000000000000000000000000000000000000000000abcdef",
        "solution": "008f2c6b5a1e2d4f9c...",
        "bits": "1d00ffff",
        "difficulty": 78421563.42,
        "previousblockhash": "00000000019cc54dbe07a2f9d0e1a6b3c8d5e4f2a1b0c9d8e7f6a5b4c3d2e1f0",
        "nextblockhash": ""
    }
}

Response Parameters

Parameter	Type	Description
hash	string	Block hash
confirmations	integer	Number of confirmations
height	integer	Block height
version	integer	Block version
merkleroot	string	Merkle root of transactions
blockcommitments	string	Block commitments hash (post-Heartwood)
finalsaplingroot	string	Final Sapling commitment tree state after this block
time	integer	Unix timestamp
nonce	string	Block nonce (hex)
solution	string	Equihash solution (hex)
bits	string	Compact difficulty target
difficulty	number	Difficulty of this block
previousblockhash	string	Parent block hash
nextblockhash	string	Next block hash (empty at chain tip)

Use Cases

• Header-First Sync: SPV clients download headers first to establish the canonical chain before fetching transactions

• Reorg Detection: Compare header hashes across polls to detect chain reorganization

• Lightweight Block Metadata: Get block timing, difficulty, and shielded-tree state without loading transactions

• Chain History Reconstruction: Iterate headers backwards from a known hash to reconstruct chain history

Error Handling

Error Code	Message	Description
-5	Block not found	Requested hash doesn't exist
-32602	Invalid params	Hash is malformed
-32603	Internal error	Node failed to retrieve the header