Send a gasless transaction

Overview

This tutorial demonstrates how to send a simple transaction using ethers.js/viem and the Biconomy Smart Account with the @biconomy/account SDK. The provided code assumes you have a Biconomy Paymaster API key.

You can get your Biconomy Paymaster API key from the dashboard here.

Prerequisites

• Node.js installed on your machine
• Biconomy Paymaster API key
• A Bundler url if you don't want to use the testnet one (for Amoy you can use https://bundler.biconomy.io/api/v2/80002/nJPK7B3ru.dd7f7861-190d-41bd-af80-6877f74b8f44)
• An rpc url (for Amoy can use https://rpc-amoy.polygon.technology/)
• An address to send the transaction to (replace 0xaddress)

Step 1: Generate the config and Create Biconomy Smart Account

viem

import { createWalletClient } from "viem";
import { privateKeyToAccount } from "viem/accounts";
import { polygonAmoy } from "viem/chains";
import { createSmartAccountClient, PaymasterMode } from "@biconomy/account";

// Your configuration with private key and Biconomy API key
const config = {
  privateKey: "your-private-key",
  biconomyPaymasterApiKey: "your-biconomy-api-key",
  bundlerUrl: "", // <-- Read about this at https://docs.biconomy.io/dashboard#bundler-url
};

// Generate EOA from private key using ethers.js
const account = privateKeyToAccount("0x" + config.privateKey);
const client = createWalletClient({
  account,
  chain: polygonAmoy,
  transport: http(),
});

// Create Biconomy Smart Account instance
const smartWallet = await createSmartAccountClient({
  signer: client,
  biconomyPaymasterApiKey: config.biconomyPaymasterApiKey,
  bundlerUrl: config.bundlerUrl,
});

const saAddress = await smartWallet.getAccountAddress();
console.log("SA Address", saAddress);

ethers

import { ethers } from "ethers";
import { createSmartAccountClient } from "@biconomy/account";

// Your configuration with private key and Biconomy API key
const config = {
  privateKey: "your-private-key",
  biconomyPaymasterApiKey: "your-biconomy-api-key",
  bundlerUrl: "", // <-- Read about this at https://docs.biconomy.io/dashboard#bundler-url
  rpcUrl: "rpc-url",
};

// Generate EOA from private key using ethers.js
let provider = new ethers.providers.JsonRpcProvider(config.rpcUrl);
let signer = new ethers.Wallet(config.privateKey, provider);

// Create Biconomy Smart Account instance
const smartWallet = await createSmartAccountClient({
  signer,
  biconomyPaymasterApiKey: config.biconomyPaymasterApiKey,
  bundlerUrl: config.bundlerUrl,
});

const saAddress = await smartWallet.getAccountAddress();
console.log("SA Address", saAddress);

Get your signer from either ethers.js or viem and create a Biconomy Smart Account instance.

Step 2: Generate Transaction Data

const toAddress = "0xaddress"; // Replace with the recipient's address
const transactionData = "0x123"; // Replace with the actual transaction data

// Build the transaction
const tx = {
  to: toAddress,
  data: transactionData,
};

Specify the recipient's address and transaction data to build the simple transaction.

Step 3: Send the Transaction and wait for the Transaction Hash

// Send the transaction and get the transaction hash
const userOpResponse = await smartWallet.sendTransaction(tx, {
  paymasterServiceData: {mode: PaymasterMode.SPONSORED},
});
const { transactionHash } = await userOpResponse.waitForTxHash();
console.log("Transaction Hash", transactionHash);
const userOpReceipt  = await userOpResponse.wait();
if(userOpReceipt.success == 'true') { 
  console.log("UserOp receipt", userOpReceipt)
  console.log("Transaction receipt", userOpReceipt.receipt)
}

Send the transaction using the Biconomy Smart Account and get the transaction hash. The transaction will be built into a User Operation and then send to the Bundler.

That's it! You've successfully sent a simple transaction using ethers.js/viem and the Biconomy Smart Account. Feel free to customize this example based on your specific use case.