getFeeForMessage - Solana

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

This method returns the fee the cluster would charge to process a base64-encoded transaction message. Fees are quoted against a specific blockhash and expire with it.

Parameters

Parameter	Type	Required	Description
message	string	Yes	Base64-encoded transaction message
config	object	No	Configuration object controlling commitment

Config Object

Field	Type	Required	Description
commitment	string	No	Commitment level: processed, confirmed, or finalized. Defaults to finalized
minContextSlot	number	No	Minimum slot the request can be evaluated at

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": "getFeeForMessage",
    "params": ["AQABAgIAAAAMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAQAA", {"commitment": "processed"}],
    "id": "getblock.io"
}'

@solana/web3.js

example.js

const { Connection } = require('@solana/web3.js');

const connection = new Connection('https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/', 'processed');

const { value: fee } = await connection.getFeeForMessage(
  transaction.compileMessage()
);

console.log(fee, 'lamports');

Request

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': 'getFeeForMessage',
        'params': ["AQABAgIAAAAMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAQAA", {"commitment": "processed"}],
        'id': 'getblock.io'
    }
)

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

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://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/")
        .header("Content-Type", "application/json")
        .json(&json!({
            "jsonrpc": "2.0",
            "method": "getFeeForMessage",
            "params": ["AQABAgIAAAAMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAQAA", {"commitment": "processed"}],
            "id": "getblock.io"
        }))
        .send()
        .await?
        .json::<Value>()
        .await?;

    println!("Result: {}", response["result"]);
    Ok(())
}

Response

{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": {
        "context": {
            "slot": 397234561
        },
        "value": 5000
    }
}

Response Parameters

Parameter	Type	Description
jsonrpc	string	JSON-RPC protocol version ("2.0")
id	string	Request identifier matching the request
result	object	RPC response object where value is the fee in lamports, or null if the blockhash has expired

Use Cases

• Fee Quotes: Show the exact lamport cost before a user signs a transaction

• Batch Sizing: Compare fees across different instruction counts in one message

• Fee Payer Checks: Confirm the fee payer balance covers the quoted amount

• Blockhash Expiry: Detect a stale blockhash when the response value is null

Error Handling

Error Code	Message	Description
-32602	Invalid params	Message is not valid base64 or cannot be deserialized
-32603	Internal error	Node failed to compute the fee for the message
-32016	Minimum context slot has not been reached	The node has not yet processed minContextSlot