ERC20 Paymaster
Available on ZKsync Era mainnet, ZKsync Sepolia, Cronos zkEVM Mainnet, Cronos zkEVM Tesnet, Abstract Tesnet.
This guide will help you get started with the Zyfi API to transform a normal transaction in a paymaster one.
For advanced usage and detailed explanation of each parameter and feature, please explore our detailed API documentation.
The basic flow consists of the following steps:
Collect the desired transaction payload and the ERC20 the user desires to pay with
Send an API request
Receive back the quote and transaction payload for the user to sign
Step 1: Send the API request
Send the required data to the erc20_paymaster
endpoint. Below an example implementation using Javascript fetch (natively supported in most environments)
// Define the payload
const payload = {
chainId: 324, // Optional, defaults to zkSync Era Mainnet; valid options are 324, 300 (ZkSync-Sepolia), 388 (Cronos zkEVM mainnet), 282 (Cronos zkEVM Tesnet) and 11124 (Abstract Testnet).
feeTokenAddress: // ERC20 the user desires to use as gas token
txData: {
from: "0x...",
to: "0x...",
data: "0x.."
}
};
// Define the function to perform the POST request
async function postTransactionData() {
try {
const response = await fetch('https://api.zyfi.org/api/erc20_paymaster/v1', {
method: 'POST',
headers: {
'Content-Type': 'application/json',
},
body: JSON.stringify(payload),
});
if (!response.ok) {
throw new Error(`HTTP error! status: ${response.status}`);
}
const data = await response.json();
console.log(data); // Process the response data
} catch (error) {
console.error('Error during the API call:', error);
}
}
The returned object does not change the original transaction calldata, but add the paymaster fields necessary to process the transaction.
Step 2: Show the quote to the user
The response, on top of the transaction payload, returns a series of helper values that can be used by the UI to better inform the user. In particular:
tokenAddress
: ERC20 token address used to pay for the gas fee (feeToken)tokenPrice
: the estimated cost of the feeTokenfeeTokenAmount
: Max amount of the ERC20 token that the user will pay as fee (before refunds). The user need to have this balance for the transaction to not failfeeUSD
: Equivalent value of feeTokenAmount in USDmarkup
: Markup or discount applied on the gas feeexpirationTime
:block.timestamp
of the quote expiration. Currently it's one hour
Step 3: Execute the transaction
Ensure you are using zksync-ethers V5 or V6.
Below an example implementation with
import { Signer, Web3Provider } from "zksync-ethers";
import * as ethers from "ethers";
const signer = Web3Provider.getSigner
rawTx = Apiresponse.txData
//since the API returns the transaction payload in the ethers format, we can use it as is
txHash = await signer.sendTransaction(rawTx);
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