Paymasters - ZKsync Docs

Besides Account Abstraction, ZKsync Era natively supports paymasters. Introduced in EIP-4337, paymasters allow to implement an intermediate step for transaction processing that can alter how the fees are being processed.

This feature can be used for things like:

Ability to pay fees in ERC20 or even NFT tokens.
Subsidizing transactions.
Managing fee payments for a static set of wallets.

...and many others.

If you want to learn about Paymaster design, see the protocol documentation.

Testnet Paymaster

To simplify development and testing, ZKsync Sepolia Testnet provides a testnet paymaster with built-in support for paying fees in ERC20 tokens.

Key details:

Address: 0x3cb2b87d10ac01736a65688f3e0fb1b070b3eea3 (see in explorer)
Chain: ZKsync Sepolia Testnet
Exchange rate: 1:1 with ETH (1 token unit = 1 wei)
Flow type: Approval-based only
Usage requirements:
- token: must match the ERC20 token used for fee payment
- minimalAllowance: must be at least tx.maxFeePerGas * tx.gasLimit
- innerInput: must be empty (0x)

Example usage:

const paymasterParams = {
  paymaster: "0x3cb2b87d10ac01736a65688f3e0fb1b070b3eea3",
  paymasterInput: {
    type: "ApprovalBased",
    token: "<ERC20_TOKEN_ADDRESS>",
    minimalAllowance: tx.maxFeePerGas * tx.gasLimit, // at least
    innerInput: "0x",
  },
};

This setup allows developers to simulate ERC20-based fee payments in a testnet environment without needing a custom paymaster deployment.

Paymaster tutorials

If you prefer learning from tutorials, you can check out the following ones:

Account Abstraction

Learn about Native Account Abstraction in ZKsync Era

Intro

Learn about ZKsync Smart Sign-on.