Gelato does not provide its own onchain paymaster, but you can use any onchain paymaster that is compatible with ERC-4337. If you’re looking to sponsor gas off-chain in a more efficient way, consider using Gas Tank.

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Using Viem

To start sponsoring transactions or paying gas fees with ERC-20 tokens with onchain paymasters using Viem, follow these steps:
1

Create a API Key

Check out our How-To Guide for detailed instructions on generating a API key.
2

Import Dependencies

import { createPublicClient, http } from 'viem'
import { createBundlerClient, createPaymasterClient, toSoladySmartAccount } from "viem/account-abstraction";
import { privateKeyToAccount } from "viem/accounts";
import { mainnet } from "viem/chains";
3

Setup Smart Account

Any smart account that implements viem’s Account type can be used here. Check out other available smart accounts here.
const publicClient = createPublicClient({ chain: mainnet, transport: http() });
const signer = privateKeyToAccount(PRIVATE_KEY as any);

const account = await toSoladySmartAccount({ 
    client: publicClient, 
    owner: signer, 
})
4

Create a Paymaster Client

Create a PaymasterClient with Paymaster URL. Learn more about Paymaster Client here.
const paymasterClient = createPaymasterClient({ 
    transport: http('Paymaster URL'), 
})
5

Create a Bundler Client

Create a BundlerClient with the account, paymasterClient and publicClient and pass the apiKey as query parameter to the transport option. Learn more about Bundler Client here.
const bundlerClient = createBundlerClient({
    account,
    paymaster: paymasterClient,
    client: publicClient,
    transport: http(`https://api.gelato.digital/bundlers/${chainID}/rpc?apiKey=${apiKey}`)
})
6

Send a UserOperation

Send a UserOperation with the bundlerClient and the account.
const userOperationHash = await bundlerClient.sendUserOperation({
    account,
    calls: [{ to: account.address, value: 0n, data: "0x" }],
})

console.log("UserOperation Hash: ", userOperationHash);

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Using Bundler API Endpoints

This is the standard method of sponsoring gas or paying gas fees with ERC-20 tokens using onchain paymasters. To use features like gas sponsorship, ERC-20 token payments, or other custom payment methods via onchain paymasters, follow these steps:
1

Create a API Key

Check out our How-To Guide for detailed instructions on generating a API key.
2

Include Paymaster Fields

You must pass all required paymaster-related fields such as paymaster, paymasterData etc. along with the standard UserOperation parameters.
3

Set `sponsored` query parameter to `false` or don't include it

When calling Gelato API endpoints, make sure to include the apiKey and sponsored set to false as a query parameter.Your Bundler URL will look like this:
https://api.gelato.digital/bundlers/${chainID}/rpc?apiKey=${apiKey}
4

Fetch Gas Parameters from Gelato APIs

Use the following endpoints to retrieve gas-related values:
  • maxFeePerGas and maxPriorityFeePerGas can be fetched from eth_getUserOperationGasPrice API Endpoint.
  • callGasLimit, verificationGasLimit, preVerificationGas & paymasterVerificationGasLimit can be fetched from eth_estimateUserOperationGas API Endpoint.
Check out the required parameters for on-chain paymasters in the following scenarios: