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Version: SDK V4 (latest)

Send a gasless transaction


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.


Step 1: Generate the config and Create Biconomy Smart Account

import { createWalletClient } from "viem";
import { privateKeyToAccount } from "viem/accounts";
import { polygonMumbai } 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

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

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.