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Send your first gasless transaction


This tutorial guides you through the process of creating a user operation, obtaining sponsorship from FuseBox's verifying paymaster, and submitting this sponsored user operation on-chain using the bundler. By leveraging FuseBox's capabilities, you can execute on-chain transactions efficiently and without the need for gas.

Obtain an API Key

Start by visiting our Operator Dashboard to generate an API key, a crucial step for accessing our services.

Clone the FuseBox Tutorial Template Repository

We've prepared a FuseBox tutorial template repository with Typescript, viem, and @fuseio/fusebox-web-sdk to help you get started. Clone the repository and prepare your development environment by executing the following commands:

git clone fusebox-tutorial
cd fusebox-tutorial
npm install

The primary file you'll be working with is index.ts. Verify your setup by running npm start; you should see Hello world! in the console.

Generate a Private Key

Securely generate and store a private key using the code snippet below in index.ts:

const privateKey =
process.env.PRIVATE_KEY ??
(() => {
const pk = generatePrivateKey();
writeFileSync(".env", `PRIVATE_KEY=${pk}`);
return pk;

Initialize the SDK

With FuseSDK, you can create User Operations for ERC-4337 Etherspot Smart Accounts, Bundler services, or Paymasters. It is open source and MIT licensed for maximum flexibility. Ensure you replace YOUR_FUSEBOX_API_KEY with your actual API key:

const apiKey = "YOUR_FUSEBOX_API_KEY";
const credentials = new ethers.Wallet(privateKey);
const fuseSDK = await FuseSDK.init(apiKey, credentials, {
withPaymaster: true,

Create a Smart Contract Wallet

Use the SDK and your private key to initialize the Etherspot Smart Account. Display the smart account address by running:

`Smart account address:${fuseSDK.wallet.getSender()}`

This smart account is counterfactual, meaning it will be deployed on-chain with your first transaction.

Submit a Transaction

Submit a transaction from the smart account to 0xd8da6bf26964af9d7eed9e03e53415d37aa96045 (vitalik.eth) using 0x1234 as the call data. The FuseSDK will facilitate this operation, including obtaining sponsorship and submission:

const to = "0xd8da6bf26964af9d7eed9e03e53415d37aa96045"; // for vitalik.eth
const value = ethers.utils.parseEther("0");
const data = new TextEncoder().encode("0x1234");
const res = await fuseSDK.callContract(to, value, data);

console.log(`UserOpHash: ${res?.userOpHash}`);
console.log("Waiting for transaction...");

const receipt = await res?.wait();

`User operation included:${receipt?.transactionHash}`

Running this will display the transaction hash and confirm your operation is on-chain.

Congratulations! You've executed a gasless transaction, deployed a smart account, verified its signature, had the operation sponsored, and performed a transaction to vitalik.eth - all seamlessly with a few lines of code.

Should you have any questions or wish to share your project, please reach out to us.