account_nextIndex - Polkadot

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

This method returns the next nonce for an account, including any transactions already queued in the pool. It is an alias of system_accountNextIndex.

Parameters

Parameter	Type	Required	Description
accountId	string	Yes	SS58 account address

Request

cURL

curl --location --request POST 'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{"jsonrpc": "2.0", "method": "account_nextIndex", "params": ["15oF4uVJwmo4TdGW7VfQxNLavjCXviqxT9S1MgbjMNHr6Sp5"], "id": "getblock.io"}'

JavaScript

example.js

const response = await fetch('https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
        jsonrpc: '2.0',
        method: 'account_nextIndex',
        params: ["15oF4uVJwmo4TdGW7VfQxNLavjCXviqxT9S1MgbjMNHr6Sp5"],
        id: 'getblock.io'
    })
});

const data = await response.json();
console.log(data.result);

Python

example.py

import requests

response = requests.post(
    'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/',
    headers={'Content-Type': 'application/json'},
    json={
        'jsonrpc': '2.0',
        'method': 'account_nextIndex',
        'params': ["15oF4uVJwmo4TdGW7VfQxNLavjCXviqxT9S1MgbjMNHr6Sp5"],
        'id': 'getblock.io'
    }
)

print(response.json()['result'])

Response

{
    "id": "getblock.io",
    "jsonrpc": "2.0",
    "result": 1234
}

Response Parameters

Parameter	Type	Description
id	string	Request identifier matching the request
jsonrpc	string	JSON-RPC protocol version ("2.0")
result	integer	The next nonce (transaction index) to use for the account

Use Cases

• Transaction Building: Set the nonce for a new extrinsic

• Sequencing: Order multiple extrinsics from one account

• Pool Awareness: Account for pending transactions in the nonce

• Wallet Backends: Compute nonces server-side before signing

Error Handling

Error Code	Message	Description
-32602	Invalid params	A parameter is missing or has the wrong type or format
-32601	Method not found	The method is not available on this endpoint
-32603	Internal error	The node failed to process the request

Library Integration

The idiomatic way to call Polkadot RPC is the Polkadot.js API (@polkadot/api), which connects over WebSocket and exposes the method as api.rpc.system.accountNextIndex.

polkadot-js.js

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

const provider = new WsProvider('wss://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/');
const api = await ApiPromise.create({ provider });

const result = await api.rpc.system.accountNextIndex('15oF4uVJwmo4TdGW7VfQxNLavjCXviqxT9S1MgbjMNHr6Sp5');
console.log(result.toHuman());