grandpa_proveFinality - Midnight

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

This method returns a GRANDPA justification proof for the specified block range, enabling light clients to independently verify finality. Provide the start of the range; the node returns the proof up to the most recent finalized block.

Parameters

Parameter

Type

Required

Description

blockNumber

integer

Yes

Block number from which to prove finality

Request Example

curl --location --request POST 'https://go.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "grandpa_proveFinality",
    "params": [
        981031
    ],
    "id": "getblock.io"
}'

import axios from 'axios';

const data = JSON.stringify({
    "jsonrpc": "2.0",
    "method": "grandpa_proveFinality",
    "params": [
        981031
    ],
    "id": "getblock.io"
});

const config = {
    method: 'post',
    url: 'https://go.getblock.io/<ACCESS-TOKEN>/',
    headers: {
        'Content-Type': 'application/json'
    },
    data: data
};

axios(config)
    .then(response => console.log(JSON.stringify(response.data, null, 2)))
    .catch(error => console.log(error));

import requests
import json

url = "https://go.getblock.io/<ACCESS-TOKEN>/"

payload = json.dumps({
    "jsonrpc": "2.0",
    "method": "grandpa_proveFinality",
    "params": [
        981031
    ],
    "id": "getblock.io"
})

headers = {
    'Content-Type': 'application/json'
}

response = requests.post(url, headers=headers, data=payload)
print(response.text)

use reqwest::Client;
use serde_json::json;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = Client::new();

    let payload = json!({
        "jsonrpc": "2.0",
        "method": "grandpa_proveFinality",
        "params": [
                981031
        ],
        "id": "getblock.io"
});

    let response = client
        .post("https://go.getblock.io/<ACCESS-TOKEN>/")
        .header("Content-Type", "application/json")
        .json(&payload)
        .send()
        .await?;

    let result: serde_json::Value = response.json().await?;
    println!("{:#?}", result);

    Ok(())
}

Response Example

{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": "0x01a3e8\u2026"
}

Response Parameters

Field

Type

Description

result

string | null

Hex-encoded GRANDPA proof, or null if no proof is available for the given range

Use Cases

Building light clients that verify finality without trusting the RPC provider
Bridging Midnight state to other chains using GRANDPA proofs
Auditing finality assumptions in security-critical applications

Error Handling

Status Code

Error Message

Cause

403

Forbidden

Missing or invalid <ACCESS-TOKEN>

-32602

Invalid params

Request parameters are missing or malformed

429

Too Many Requests

Rate limit exceeded for your plan

SDK Integration

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

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

// Call via the typed API:
const result = await api.rpc.grandpa.proveFinality(981031);
console.log(result.toJSON());

// Or call the raw JSON-RPC method:
const raw = await api.rpc.rpc.methods();
// const raw = await (api as any)._rpcCore.provider.send('grandpa_proveFinality', [981031]);

from substrateinterface import SubstrateInterface

substrate = SubstrateInterface(url='wss://go.getblock.io/<ACCESS-TOKEN>/')

# Generic RPC call:
result = substrate.rpc_request('grandpa_proveFinality', [981031])
print(result)

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