Simulate sending a transaction

POST

https://sol.nownodes.io/

Authorizations

ApiKeyAuthApiKeyAuth

api-key string

NOWNodes API key passed in the api-key header.

JSON-RPC method for simulating transactions

Body

application/json

JSON-RPC method for simulating transactions

Object containing request fields.

jsonrpcstringrequired

JSON-RPC protocol version.

methodstringrequired

Solana JSON-RPC method name.

paramsArray<string | object>required

Ordered positional parameters for the Solana JSON-RPC method:

Signed or unsigned transaction encoded as base64 or base58 for simulation.
Optional transaction simulation configuration object.

Show child attributes

One positional parameter. The expected meaning depends on its array index; see params.description.

Any of

Signed or unsigned transaction encoded as base64 or base58 for simulation.

string

sigVerifyboolean

Whether to verify transaction signatures during simulation.

replaceRecentBlockhashboolean

Whether to replace the recent blockhash before simulation.

commitmentstring

Bank commitment level used to evaluate the simulation.

encodingstring

Encoding of the transaction payload.

accountsobject

Optional account data selection to return after simulation.

Show child attributes

encodingstring

Encoding format for returned account data.

addressesArray<string>

Account addresses to return after simulation.

minContextSlotinteger

Minimum slot that the request can be evaluated at.

idintegerrequired

Client request identifier echoed by the server.

Response

200OK

Transaction simulation result

400Bad Request

Bad Request. The Solana JSON-RPC request is malformed or contains invalid parameters.

401Unauthorized

Unauthorized: API key is present but rejected by the NOWNodes gateway.

405Method Not Allowed

Method Not Allowed. Returned by the NOWNodes gateway for malformed or unsupported gateway-level requests.

422Unprocessable Entity

Missing API key. The NOWNodes gateway returns plain text for this error.

500Internal Server Error

Internal Server Error. The gateway or Solana node failed while processing the request.

Simulate sending a transaction

curl -X POST 'https://sol.nownodes.io/' \
  -H 'Content-Type: application/json' \
  -d '{
    "jsonrpc": "2.0",
    "method": "simulateTransaction",
    "params": [
      "4hXTCkRzt9WyecNzV1XPgCDfGAZzQKNxLXgynz5QDuWWPSAZBZSHptvWRL3BjCvzUXRdKvHL2b7yGrRQcWyaqsaBCncVG7BFggS8w9snUts67BSh3EqKpXLUm5UMHfD7ZBe9GhARjbNQMLJ1QD3Spr6oMTBU6EhdB4RD8CP2xUxr2u3d6fos36PD98XS6oX8TQjLpsMwncs5DAMiD4nNnR8NBfyghGCWvCVifVwvA8B8TJxE1aiyiv2L429BCWfyzAme5sZW8rDb14NeCQHhZbtNqfXhcp2tAnaAT",
      {
        "encoding": "base64",
        "replaceRecentBlockhash": true,
        "sigVerify": false
      }
    ],
    "id": 1
  }'

import { JsonRpcProvider } from "ethers";

const provider = new JsonRpcProvider("https://sol.nownodes.io/");
const result = await provider.send("simulateTransaction", [
  "4hXTCkRzt9WyecNzV1XPgCDfGAZzQKNxLXgynz5QDuWWPSAZBZSHptvWRL3BjCvzUXRdKvHL2b7yGrRQcWyaqsaBCncVG7BFggS8w9snUts67BSh3EqKpXLUm5UMHfD7ZBe9GhARjbNQMLJ1QD3Spr6oMTBU6EhdB4RD8CP2xUxr2u3d6fos36PD98XS6oX8TQjLpsMwncs5DAMiD4nNnR8NBfyghGCWvCVifVwvA8B8TJxE1aiyiv2L429BCWfyzAme5sZW8rDb14NeCQHhZbtNqfXhcp2tAnaAT",
  {
    "encoding": "base64",
    "replaceRecentBlockhash": true,
    "sigVerify": false
  }
]);
console.log(result);

require 'eth'
require 'json'
require 'net/http'

uri = URI('https://sol.nownodes.io/')
request = Net::HTTP::Post.new(uri)
request['Content-Type'] = 'application/json'
request.body = '{
  "jsonrpc": "2.0",
  "method": "simulateTransaction",
  "params": [
    "4hXTCkRzt9WyecNzV1XPgCDfGAZzQKNxLXgynz5QDuWWPSAZBZSHptvWRL3BjCvzUXRdKvHL2b7yGrRQcWyaqsaBCncVG7BFggS8w9snUts67BSh3EqKpXLUm5UMHfD7ZBe9GhARjbNQMLJ1QD3Spr6oMTBU6EhdB4RD8CP2xUxr2u3d6fos36PD98XS6oX8TQjLpsMwncs5DAMiD4nNnR8NBfyghGCWvCVifVwvA8B8TJxE1aiyiv2L429BCWfyzAme5sZW8rDb14NeCQHhZbtNqfXhcp2tAnaAT",
    {
      "encoding": "base64",
      "replaceRecentBlockhash": true,
      "sigVerify": false
    }
  ],
  "id": 1
}'

response = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) do |http|
  http.request(request)
end

puts JSON.parse(response.body)

from web3 import Web3

w3 = Web3(Web3.HTTPProvider("https://sol.nownodes.io/"))
response = w3.provider.make_request("simulateTransaction", [
  "4hXTCkRzt9WyecNzV1XPgCDfGAZzQKNxLXgynz5QDuWWPSAZBZSHptvWRL3BjCvzUXRdKvHL2b7yGrRQcWyaqsaBCncVG7BFggS8w9snUts67BSh3EqKpXLUm5UMHfD7ZBe9GhARjbNQMLJ1QD3Spr6oMTBU6EhdB4RD8CP2xUxr2u3d6fos36PD98XS6oX8TQjLpsMwncs5DAMiD4nNnR8NBfyghGCWvCVifVwvA8B8TJxE1aiyiv2L429BCWfyzAme5sZW8rDb14NeCQHhZbtNqfXhcp2tAnaAT",
  {
    "encoding": "base64",
    "replaceRecentBlockhash": True,
    "sigVerify": False
  }
])
print(response)

import { createPublicClient, http } from "viem";

const client = createPublicClient({
  transport: http("https://sol.nownodes.io/"),
});

const result = await client.request({
  method: "simulateTransaction",
  params: [
  "4hXTCkRzt9WyecNzV1XPgCDfGAZzQKNxLXgynz5QDuWWPSAZBZSHptvWRL3BjCvzUXRdKvHL2b7yGrRQcWyaqsaBCncVG7BFggS8w9snUts67BSh3EqKpXLUm5UMHfD7ZBe9GhARjbNQMLJ1QD3Spr6oMTBU6EhdB4RD8CP2xUxr2u3d6fos36PD98XS6oX8TQjLpsMwncs5DAMiD4nNnR8NBfyghGCWvCVifVwvA8B8TJxE1aiyiv2L429BCWfyzAme5sZW8rDb14NeCQHhZbtNqfXhcp2tAnaAT",
  {
    "encoding": "base64",
    "replaceRecentBlockhash": true,
    "sigVerify": false
  }
],
});

console.log(result);

const endpoint = "https://sol.nownodes.io/";
const apiKey = "YOUR_API_KEY";

async function nownodesRequest(payload) {
  const response = await fetch(endpoint, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "api-key": apiKey,
    },
    body: JSON.stringify(payload),
  });

  return response.json();
}

const result = await nownodesRequest({ jsonrpc: "2.0", method: "simulateTransaction", params: [
  "4hXTCkRzt9WyecNzV1XPgCDfGAZzQKNxLXgynz5QDuWWPSAZBZSHptvWRL3BjCvzUXRdKvHL2b7yGrRQcWyaqsaBCncVG7BFggS8w9snUts67BSh3EqKpXLUm5UMHfD7ZBe9GhARjbNQMLJ1QD3Spr6oMTBU6EhdB4RD8CP2xUxr2u3d6fos36PD98XS6oX8TQjLpsMwncs5DAMiD4nNnR8NBfyghGCWvCVifVwvA8B8TJxE1aiyiv2L429BCWfyzAme5sZW8rDb14NeCQHhZbtNqfXhcp2tAnaAT",
  {
    "encoding": "base64",
    "replaceRecentBlockhash": true,
    "sigVerify": false
  }
], id: 1 });
console.log(result);

const response = await fetch('https://sol.nownodes.io/', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
      "jsonrpc": "2.0",
      "method": "simulateTransaction",
      "params": [
        "4hXTCkRzt9WyecNzV1XPgCDfGAZzQKNxLXgynz5QDuWWPSAZBZSHptvWRL3BjCvzUXRdKvHL2b7yGrRQcWyaqsaBCncVG7BFggS8w9snUts67BSh3EqKpXLUm5UMHfD7ZBe9GhARjbNQMLJ1QD3Spr6oMTBU6EhdB4RD8CP2xUxr2u3d6fos36PD98XS6oX8TQjLpsMwncs5DAMiD4nNnR8NBfyghGCWvCVifVwvA8B8TJxE1aiyiv2L429BCWfyzAme5sZW8rDb14NeCQHhZbtNqfXhcp2tAnaAT",
        {
          "encoding": "base64",
          "replaceRecentBlockhash": true,
          "sigVerify": false
        }
      ],
      "id": 1
    }),
});

const data = await response.json();

import requests

payload = {
  "jsonrpc": "2.0",
  "method": "simulateTransaction",
  "params": [
    "4hXTCkRzt9WyecNzV1XPgCDfGAZzQKNxLXgynz5QDuWWPSAZBZSHptvWRL3BjCvzUXRdKvHL2b7yGrRQcWyaqsaBCncVG7BFggS8w9snUts67BSh3EqKpXLUm5UMHfD7ZBe9GhARjbNQMLJ1QD3Spr6oMTBU6EhdB4RD8CP2xUxr2u3d6fos36PD98XS6oX8TQjLpsMwncs5DAMiD4nNnR8NBfyghGCWvCVifVwvA8B8TJxE1aiyiv2L429BCWfyzAme5sZW8rDb14NeCQHhZbtNqfXhcp2tAnaAT",
    {
      "encoding": "base64",
      "replaceRecentBlockhash": True,
      "sigVerify": False
    }
  ],
  "id": 1
}

response = requests.post('https://sol.nownodes.io/', json=payload)
data = response.json()

require 'net/http'
require 'json'

uri = URI('https://sol.nownodes.io/')
request = Net::HTTP::Post.new(uri)
request['Content-Type'] = 'application/json'
request.body = '{
    "jsonrpc": "2.0",
    "method": "simulateTransaction",
    "params": [
      "4hXTCkRzt9WyecNzV1XPgCDfGAZzQKNxLXgynz5QDuWWPSAZBZSHptvWRL3BjCvzUXRdKvHL2b7yGrRQcWyaqsaBCncVG7BFggS8w9snUts67BSh3EqKpXLUm5UMHfD7ZBe9GhARjbNQMLJ1QD3Spr6oMTBU6EhdB4RD8CP2xUxr2u3d6fos36PD98XS6oX8TQjLpsMwncs5DAMiD4nNnR8NBfyghGCWvCVifVwvA8B8TJxE1aiyiv2L429BCWfyzAme5sZW8rDb14NeCQHhZbtNqfXhcp2tAnaAT",
      {
        "encoding": "base64",
        "replaceRecentBlockhash": true,
        "sigVerify": false
      }
    ],
    "id": 1
  }'

response = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) { |http| http.request(request) }
data = JSON.parse(response.body)

Request Body

{
  "jsonrpc": "2.0",
  "method": "simulateTransaction",
  "params": [
    "4hXTCkRzt9WyecNzV1XPgCDfGAZzQKNxLXgynz5QDuWWPSAZBZSHptvWRL3BjCvzUXRdKvHL2b7yGrRQcWyaqsaBCncVG7BFggS8w9snUts67BSh3EqKpXLUm5UMHfD7ZBe9GhARjbNQMLJ1QD3Spr6oMTBU6EhdB4RD8CP2xUxr2u3d6fos36PD98XS6oX8TQjLpsMwncs5DAMiD4nNnR8NBfyghGCWvCVifVwvA8B8TJxE1aiyiv2L429BCWfyzAme5sZW8rDb14NeCQHhZbtNqfXhcp2tAnaAT",
    {
      "encoding": "base64",
      "replaceRecentBlockhash": true,
      "sigVerify": false
    }
  ],
  "id": 1
}

{
  "jsonrpc": "2.0",
  "result": {
    "context": {
      "slot": 350000000
    },
    "value": {
      "err": null,
      "logs": [
        "Program log: simulated"
      ],
      "unitsConsumed": 1500,
      "accounts": null,
      "returnData": null
    }
  },
  "id": 1
}

{
  "jsonrpc": "2.0",
  "error": {
    "code": -32602,
    "message": "Invalid params"
  },
  "id": 1
}

{
  "jsonrpc": "2.0",
  "error": {
    "code": -32602,
    "message": "Invalid params",
    "data": "Invalid param: wrong number of parameters"
  },
  "id": 1
}

Unknown API_key

Method Not Allowed

Missing API_key

{
  "jsonrpc": "2.0",
  "error": {
    "code": -32000,
    "message": "Internal error",
    "data": "Solana node failed to process the request"
  },
  "id": 1
}

Documentation

How to migrate to NOWNodes

Simulate sending a transaction

Authorizations

Body

Response