Simulate transactions with eth_simulateV1

POST

https://monad.nownodes.io/

Authorizations

ApiKeyAuthApiKeyAuth

api-key string

NOWNodes API key passed in the api-key header.

Simulates one or more calls against a selected block state. The request may include state overrides and transfer tracing.

Body

application/json

JSON-RPC request body for the eth_simulateV1 method.

jsonrpcstringrequired

JSON-RPC protocol version. Must be 2.0.

idintegerrequired

Client-defined request identifier returned unchanged in the response.

methodstringrequired

JSON-RPC method name.

paramsArray<object | string>required

Parameters for eth_simulateV1. The first item contains simulation options. The second item defines the base block tag.

Show child attributes

One of

blockStateCallsArray<object>required

List of simulated block state calls.

Show child attributes

stateOverridesobject

State override map keyed by account address. Each key is an Ethereum-style address whose state should be overridden.

callsArray<object>required

List of calls to simulate in the block state context.

Show child attributes

fromstringrequired

Sender address used for the simulated call.

tostringrequired

Recipient address or contract address targeted by the simulated call.

gasstring

Maximum gas provided for the simulated call, encoded as a hexadecimal quantity.

valuestring

Native token value transferred by the simulated call, encoded as a hexadecimal quantity.

datastring

Optional calldata for contract execution, encoded as a hexadecimal string.

inputstring

Optional calldata alias used by some Ethereum-compatible clients.

gasPricestring

Optional legacy gas price, encoded as a hexadecimal quantity.

maxFeePerGasstring

Optional EIP-1559 maximum fee per gas, encoded as a hexadecimal quantity. If validation is enabled, this value must be greater than or equal to the block base fee.

maxPriorityFeePerGasstring

Optional EIP-1559 priority fee per gas, encoded as a hexadecimal quantity.

traceTransfersboolean

Enables transfer tracing in the simulation result.

validationboolean

Enables transaction validation during simulation. When enabled, simulated calls must satisfy validation rules such as gas fee checks.

Block tag or block identifier used as the base state for simulation.

string

Response

200OK

Successful JSON-RPC response containing simulated block execution results.

400Bad Request

Invalid JSON-RPC request.

Simulate transactions with eth_simulateV1

curl -X POST 'https://monad.nownodes.io/' \
  -H 'Content-Type: application/json' \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "eth_simulateV1",
    "params": [
      {
        "blockStateCalls": [
          {
            "stateOverrides": {},
            "calls": [
              {
                "from": "0xc000000000000000000000000000000000000000",
                "to": "0xc000000000000000000000000000000000000001",
                "gas": "0x5208",
                "value": "0x1",
                "data": "0x",
                "input": "0x",
                "gasPrice": "0x3b9aca00",
                "maxFeePerGas": "0x2540be400",
                "maxPriorityFeePerGas": "0x3b9aca00"
              }
            ]
          }
        ],
        "traceTransfers": true,
        "validation": false
      }
    ]
  }'

import { JsonRpcProvider } from "ethers";

const provider = new JsonRpcProvider("https://monad.nownodes.io/");
const result = await provider.send("eth_simulateV1", [
  {
    "blockStateCalls": [
      {
        "stateOverrides": {},
        "calls": [
          {
            "from": "0xc000000000000000000000000000000000000000",
            "to": "0xc000000000000000000000000000000000000001",
            "gas": "0x5208",
            "value": "0x1",
            "data": "0x",
            "input": "0x",
            "gasPrice": "0x3b9aca00",
            "maxFeePerGas": "0x2540be400",
            "maxPriorityFeePerGas": "0x3b9aca00"
          }
        ]
      }
    ],
    "traceTransfers": true,
    "validation": false
  }
]);
console.log(result);

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

uri = URI('https://monad.nownodes.io/')
request = Net::HTTP::Post.new(uri)
request['Content-Type'] = 'application/json'
request.body = '{
  "jsonrpc": "2.0",
  "method": "eth_simulateV1",
  "params": [
    {
      "blockStateCalls": [
        {
          "stateOverrides": {},
          "calls": [
            {
              "from": "0xc000000000000000000000000000000000000000",
              "to": "0xc000000000000000000000000000000000000001",
              "gas": "0x5208",
              "value": "0x1",
              "data": "0x",
              "input": "0x",
              "gasPrice": "0x3b9aca00",
              "maxFeePerGas": "0x2540be400",
              "maxPriorityFeePerGas": "0x3b9aca00"
            }
          ]
        }
      ],
      "traceTransfers": true,
      "validation": 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://monad.nownodes.io/"))
response = w3.provider.make_request("eth_simulateV1", [
  {
    "blockStateCalls": [
      {
        "stateOverrides": {},
        "calls": [
          {
            "from": "0xc000000000000000000000000000000000000000",
            "to": "0xc000000000000000000000000000000000000001",
            "gas": "0x5208",
            "value": "0x1",
            "data": "0x",
            "input": "0x",
            "gasPrice": "0x3b9aca00",
            "maxFeePerGas": "0x2540be400",
            "maxPriorityFeePerGas": "0x3b9aca00"
          }
        ]
      }
    ],
    "traceTransfers": True,
    "validation": False
  }
])
print(response)

import { createPublicClient, http } from "viem";

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

const result = await client.request({
  method: "eth_simulateV1",
  params: [
  {
    "blockStateCalls": [
      {
        "stateOverrides": {},
        "calls": [
          {
            "from": "0xc000000000000000000000000000000000000000",
            "to": "0xc000000000000000000000000000000000000001",
            "gas": "0x5208",
            "value": "0x1",
            "data": "0x",
            "input": "0x",
            "gasPrice": "0x3b9aca00",
            "maxFeePerGas": "0x2540be400",
            "maxPriorityFeePerGas": "0x3b9aca00"
          }
        ]
      }
    ],
    "traceTransfers": true,
    "validation": false
  }
],
});

console.log(result);

const endpoint = "https://monad.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: "eth_simulateV1", params: [
  {
    "blockStateCalls": [
      {
        "stateOverrides": {},
        "calls": [
          {
            "from": "0xc000000000000000000000000000000000000000",
            "to": "0xc000000000000000000000000000000000000001",
            "gas": "0x5208",
            "value": "0x1",
            "data": "0x",
            "input": "0x",
            "gasPrice": "0x3b9aca00",
            "maxFeePerGas": "0x2540be400",
            "maxPriorityFeePerGas": "0x3b9aca00"
          }
        ]
      }
    ],
    "traceTransfers": true,
    "validation": false
  }
], id: 1 });
console.log(result);

const response = await fetch('https://monad.nownodes.io/', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
      "jsonrpc": "2.0",
      "id": 1,
      "method": "eth_simulateV1",
      "params": [
        {
          "blockStateCalls": [
            {
              "stateOverrides": {},
              "calls": [
                {
                  "from": "0xc000000000000000000000000000000000000000",
                  "to": "0xc000000000000000000000000000000000000001",
                  "gas": "0x5208",
                  "value": "0x1",
                  "data": "0x",
                  "input": "0x",
                  "gasPrice": "0x3b9aca00",
                  "maxFeePerGas": "0x2540be400",
                  "maxPriorityFeePerGas": "0x3b9aca00"
                }
              ]
            }
          ],
          "traceTransfers": true,
          "validation": false
        }
      ]
    }),
});

const data = await response.json();

import requests

payload = {
  "jsonrpc": "2.0",
  "id": 1,
  "method": "eth_simulateV1",
  "params": [
    {
      "blockStateCalls": [
        {
          "stateOverrides": {},
          "calls": [
            {
              "from": "0xc000000000000000000000000000000000000000",
              "to": "0xc000000000000000000000000000000000000001",
              "gas": "0x5208",
              "value": "0x1",
              "data": "0x",
              "input": "0x",
              "gasPrice": "0x3b9aca00",
              "maxFeePerGas": "0x2540be400",
              "maxPriorityFeePerGas": "0x3b9aca00"
            }
          ]
        }
      ],
      "traceTransfers": True,
      "validation": False
    }
  ]
}

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

require 'net/http'
require 'json'

uri = URI('https://monad.nownodes.io/')
request = Net::HTTP::Post.new(uri)
request['Content-Type'] = 'application/json'
request.body = '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "eth_simulateV1",
    "params": [
      {
        "blockStateCalls": [
          {
            "stateOverrides": {},
            "calls": [
              {
                "from": "0xc000000000000000000000000000000000000000",
                "to": "0xc000000000000000000000000000000000000001",
                "gas": "0x5208",
                "value": "0x1",
                "data": "0x",
                "input": "0x",
                "gasPrice": "0x3b9aca00",
                "maxFeePerGas": "0x2540be400",
                "maxPriorityFeePerGas": "0x3b9aca00"
              }
            ]
          }
        ],
        "traceTransfers": true,
        "validation": false
      }
    ]
  }'

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",
  "id": 1,
  "method": "eth_simulateV1",
  "params": [
    {
      "blockStateCalls": [
        {
          "stateOverrides": {},
          "calls": [
            {
              "from": "0xc000000000000000000000000000000000000000",
              "to": "0xc000000000000000000000000000000000000001",
              "gas": "0x5208",
              "value": "0x1",
              "data": "0x",
              "input": "0x",
              "gasPrice": "0x3b9aca00",
              "maxFeePerGas": "0x2540be400",
              "maxPriorityFeePerGas": "0x3b9aca00"
            }
          ]
        }
      ],
      "traceTransfers": true,
      "validation": false
    }
  ]
}

{
  "jsonrpc": "2.0",
  "result": [
    {
      "hash": "0xdb4fac87c55473bd5611ab5f48e365f0bc969d73c3690d8329d3ed23cdc107cb",
      "size": "0x24a",
      "calls": [
        {
          "logs": [
            {
              "data": "0x0000000000000000000000000000000000000000000000000000000000000001",
              "topics": [
                "0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef"
              ],
              "address": "0xeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee",
              "removed": false,
              "logIndex": "0x0",
              "blockHash": "0xdb4fac87c55473bd5611ab5f48e365f0bc969d73c3690d8329d3ed23cdc107cb",
              "blockNumber": "0x4fbc5ca",
              "transactionHash": "0xb212d37a41f995b3953b122ea433c42c8e0f0d79538289e3f0c05e733db39ae5",
              "transactionIndex": "0x0"
            }
          ],
          "status": "0x1",
          "gasUsed": "0x5208",
          "returnData": "0x"
        }
      ],
      "miner": "0xf23317ce1f94b1dab943129f39c869159199deed",
      "nonce": "0x0000000000000000",
      "number": "0x4fbc5ca",
      "uncles": [
        "0x0000000000000000000000000000000000000000000000000000000000000000"
      ],
      "gasUsed": "0x5208",
      "mixHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
      "gasLimit": "0xbebc200",
      "extraData": "0x",
      "logsBloom": "0x00000200000000000000000000200000001000000000000000000000000021000000000000000000000000000000000000000000000000000000000000000000000000000000000000008000000000000000000040000000000000000000000000000000000000000000000000000000000000000000000000000010000010000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000040000000002000000000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000",
      "stateRoot": "0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421",
      "timestamp": "0x6a3d2c71",
      "difficulty": "0x0",
      "parentHash": "0xc5ff1e195f6ae1725f6701993e6cc14c8c252182e5e036d85693a2fa695d49c4",
      "sha3Uncles": "0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347",
      "withdrawals": [
        {
          "index": "0x0",
          "validatorIndex": "0x0",
          "address": "0x0000000000000000000000000000000000000000",
          "amount": "0x0"
        }
      ],
      "receiptsRoot": "0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421",
      "transactions": [
        "0xb212d37a41f995b3953b122ea433c42c8e0f0d79538289e3f0c05e733db39ae5"
      ],
      "baseFeePerGas": "0x0",
      "withdrawalsRoot": "0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470",
      "transactionsRoot": "0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421"
    }
  ],
  "id": 1
}

{
  "jsonrpc": "2.0",
  "error": {
    "code": -32603,
    "message": "max fee per gas less than block base fee"
  },
  "id": 1
}

Documentation

How to migrate to NOWNodes

Simulate transactions with eth_simulateV1

Authorizations

Body

Response