testmempoolaccept - Bitcoin Cash

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

This method checks whether a raw transaction would be accepted into the mempool without actually submitting it. It is a dry run for broadcast.

Parameters

Parameter	Type	Required	Description
rawtxs	array	Yes	Array of raw transaction hex strings, currently limited to one
maxfeerate	numeric or string	No	Reject if fee rate exceeds this value, in BCH per kB. Default 0.10

Request

cURL

curl --location --request POST 'https://go.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "testmempoolaccept",
    "params": [["01000000000101e17e03d21d051aa2bd9d336c3ac0693cfa92ce71592ceec521b1c48019ff77a101000000171600146d76e574b5f4825fe740ba6c41aaf1b319dfb80cffffffff02819a010000000000160014422002d927a1cae901eac668444cce8dd0ae60d529b31b0b0000000017a914f5b48d1130dc3d366d1eabf6783a552d1c8e08f487000000000"], null],
    "id": "getblock.io"
}'

bitcoinjs-lib

example.js

const axios = require('axios');
const { data } = await axios.post('https://go.getblock.io/<ACCESS-TOKEN>/', {
  jsonrpc: '2.0', method: 'testmempoolaccept',
  params: [[rawTxHex], null], id: 'getblock.io'
});
console.log(data.result[0].allowed);

Request

example.py

import requests

response = requests.post(
    'https://go.getblock.io/<ACCESS-TOKEN>/',
    headers={'Content-Type': 'application/json'},
    json={
        'jsonrpc': '2.0',
        'method': 'testmempoolaccept',
        'params': [["01000000000101e17e03d21d051aa2bd9d336c3ac0693cfa92ce71592ceec521b1c48019ff77a101000000171600146d76e574b5f4825fe740ba6c41aaf1b319dfb80cffffffff02819a010000000000160014422002d927a1cae901eac668444cce8dd0ae60d529b31b0b0000000017a914f5b48d1130dc3d366d1eabf6783a552d1c8e08f487000000000"], null],
        '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://go.getblock.io/<ACCESS-TOKEN>/")
        .header("Content-Type", "application/json")
        .json(&json!({
            "jsonrpc": "2.0",
            "method": "testmempoolaccept",
            "params": [["01000000000101e17e03d21d051aa2bd9d336c3ac0693cfa92ce71592ceec521b1c48019ff77a101000000171600146d76e574b5f4825fe740ba6c41aaf1b319dfb80cffffffff02819a010000000000160014422002d927a1cae901eac668444cce8dd0ae60d529b31b0b0000000017a914f5b48d1130dc3d366d1eabf6783a552d1c8e08f487000000000"], null],
            "id": "getblock.io"
        }))
        .send()
        .await?
        .json::<Value>()
        .await?;

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

Response

{
    "error": null,
    "id": "getblock.io",
    "result": [
        {
            "txid": "10b54fd708ab2e5703979b4ba27ca0339882abc2062e77fbe51e625203a49642",
            "allowed": true,
            "size": 223,
            "fees": {
                "base": 2.26e-06
            }
        }
    ]
}

Response Parameters

Parameter	Type	Description
error	null|object	Error object when the call fails, otherwise null
id	string	Request identifier matching the request
result	array	Array with one acceptance-test result per supplied transaction

Result Entry

Field	Type	Description
txid	string	The transaction id
allowed	boolean	Whether the transaction would be accepted
reject-reason	string	Reason for rejection when allowed is false
fees	object	Fee details for the transaction

Use Cases

• Pre-Send Validation: Confirm a transaction is relayable before broadcasting

• Fee Checks: Detect fee-rate rejections before paying to send

• Policy Testing: Verify a transaction meets mempool policy rules

• Wallet UX: Warn a user of rejection reasons before submission

Error Handling

Error Code	Message	Description
-22	TX decode failed	The raw transaction hex could not be decoded
-26	Transaction rejected	The transaction failed mempool acceptance checks
-25	Missing inputs	One or more referenced inputs do not exist or are already spent
-32603	Internal error	Node failed to process the transaction