check_tx - Cosmos

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

Runs CheckTx against the application without broadcasting the transaction to the network. Use this to validate a signed transaction before deciding to broadcast — checks signature, sequence, fees, etc.

Parameters

Parameter

Type

Required

Description

string

Yes

Base64-encoded signed transaction bytes

Request Example

# JSON-RPC over HTTP POST (canonical)
curl --location --request POST 'https://go.getblock.io/<ACCESS-TOKEN>/check_tx' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "check_tx",
    "params": {
        "tx": "Co0BCooBChwvY29zbW9zLmJhbmsudjFiZXRhMS5Nc2dTZW5kEmoKLWNvc21vczF0NnJsZ2Y4MGpkOHRhbnBubnZtbXhmcWRjbTljbjd3Y3RyczdoaxItY29zbW9zMWdoZDc1M3NoamVjajRpdjJ4Mmk4eHJrenphbnpqdnZjMjJ4MmtuGgoKBXVhdG9tEgExEnIKWg=="
    },
    "id": "getblock.io"
}'

# URI over HTTP GET (alternate, for simple methods)
curl --location --request GET 'https://go.getblock.io/<ACCESS-TOKEN>/check_tx?tx="Co0BCooBChwvY29zbW9zLmJhbmsudjFiZXRhMS5Nc2dTZW5kEmoKLWNvc21vczF0NnJsZ2Y4MGpkOHRhbnBubnZtbXhmcWRjbTljbjd3Y3RyczdoaxItY29zbW9zMWdoZDc1M3NoamVjajRpdjJ4Mmk4eHJrenphbnpqdnZjMjJ4MmtuGgoKBXVhdG9tEgExEnIKWg=="'

import axios from 'axios';

const data = JSON.stringify({
    "jsonrpc": "2.0",
    "method": "check_tx",
    "params": {
        "tx": "Co0BCooBChwvY29zbW9zLmJhbmsudjFiZXRhMS5Nc2dTZW5kEmoKLWNvc21vczF0NnJsZ2Y4MGpkOHRhbnBubnZtbXhmcWRjbTljbjd3Y3RyczdoaxItY29zbW9zMWdoZDc1M3NoamVjajRpdjJ4Mmk4eHJrenphbnpqdnZjMjJ4MmtuGgoKBXVhdG9tEgExEnIKWg=="
    },
    "id": "getblock.io"
});

const config = {
    method: 'post',
    url: 'https://go.getblock.io/<ACCESS-TOKEN>/check_tx',
    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>/check_tx"

payload = json.dumps({
    "jsonrpc": "2.0",
    "method": "check_tx",
    "params": {
        "tx": "Co0BCooBChwvY29zbW9zLmJhbmsudjFiZXRhMS5Nc2dTZW5kEmoKLWNvc21vczF0NnJsZ2Y4MGpkOHRhbnBubnZtbXhmcWRjbTljbjd3Y3RyczdoaxItY29zbW9zMWdoZDc1M3NoamVjajRpdjJ4Mmk4eHJrenphbnpqdnZjMjJ4MmtuGgoKBXVhdG9tEgExEnIKWg=="
    },
    "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": "check_tx",
        "params": {
                "tx": "Co0BCooBChwvY29zbW9zLmJhbmsudjFiZXRhMS5Nc2dTZW5kEmoKLWNvc21vczF0NnJsZ2Y4MGpkOHRhbnBubnZtbXhmcWRjbTljbjd3Y3RyczdoaxItY29zbW9zMWdoZDc1M3NoamVjajRpdjJ4Mmk4eHJrenphbnpqdnZjMjJ4MmtuGgoKBXVhdG9tEgExEnIKWg=="
        },
        "id": "getblock.io"
});

    let response = client
        .post("https://go.getblock.io/<ACCESS-TOKEN>/check_tx")
        .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": {
        "code": 0,
        "data": "",
        "log": "",
        "gas_wanted": "200000",
        "gas_used": "0",
        "events": [],
        "codespace": ""
    }
}

Response Parameters

Field

Type

Description

result.code

integer

0 if the transaction would be accepted

result.log

string

Failure reason if code is non-zero

result.gas_wanted

string

Gas limit declared by the transaction

result.codespace

string

Module codespace for non-zero codes

Use Cases

Pre-flight transaction validation in wallets
Simulating transactions for fee estimation
Debugging signing failures before broadcast

Error Handling

Status Code

Error Message

Cause

404

Not found

Missing or invalid <ACCESS-TOKEN>

-32602

Invalid params

Request parameters are missing or malformed

-32603

Internal error

Server-side error while processing the request

429

Too Many Requests

Rate limit exceeded for your plan

SDK Integration

import { Tendermint37Client, HttpClient } from '@cosmjs/tendermint-rpc';

const httpClient = new HttpClient('https://go.getblock.io/<ACCESS-TOKEN>/');
const client = await Tendermint37Client.create(httpClient);

// CosmJS exposes typed methods on the client (e.g. client.status(), client.block()).
// For raw access to any RPC method:
const result = await httpClient.execute({"jsonrpc": "2.0", "id": "getblock.io", "method": "check_tx", "params": {"tx": "Co0BCooBChwvY29zbW9zLmJhbmsudjFiZXRhMS5Nc2dTZW5kEmoKLWNvc21vczF0NnJsZ2Y4MGpkOHRhbnBubnZtbXhmcWRjbTljbjd3Y3RyczdoaxItY29zbW9zMWdoZDc1M3NoamVjajRpdjJ4Mmk4eHJrenphbnpqdnZjMjJ4MmtuGgoKBXVhdG9tEgExEnIKWg=="}});
console.log(result);

# cosmpy wraps Cosmos REST / gRPC. For raw CometBFT RPC access, use requests.
import requests

response = requests.post('https://go.getblock.io/<ACCESS-TOKEN>/', json={
    'jsonrpc': '2.0',
    'id': 'getblock.io',
    'method': 'check_tx',
    'params': {"tx": "Co0BCooBChwvY29zbW9zLmJhbmsudjFiZXRhMS5Nc2dTZW5kEmoKLWNvc21vczF0NnJsZ2Y4MGpkOHRhbnBubnZtbXhmcWRjbTljbjd3Y3RyczdoaxItY29zbW9zMWdoZDc1M3NoamVjajRpdjJ4Mmk4eHJrenphbnpqdnZjMjJ4MmtuGgoKBXVhdG9tEgExEnIKWg=="}
}})
print(response.json())

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