> ## Documentation Index
> Fetch the complete documentation index at: https://voltaire.tevm.sh/llms.txt
> Use this file to discover all available pages before exploring further.

# Paymaster

> ERC-4337 paymaster contract address type

# Paymaster

Paymaster is a branded [Address](/primitives/address) type representing an ERC-4337 paymaster contract. Paymasters sponsor gas fees for user operations, enabling gasless transactions or allowing users to pay gas in ERC-20 tokens.

## Quick Start

```typescript theme={null}
import { Paymaster } from '@tevm/voltaire/primitives/Paymaster';

// Create paymaster address
const paymaster = Paymaster.from("0x742d35Cc6634C0532925a3b844Bc9e7595f251e3");

// Convert to hex
console.log(Paymaster.toHex(paymaster));
// "0x742d35cc6634c0532925a3b844bc9e7595f251e3"

// Compare addresses
const same = Paymaster.equals(paymaster, "0x742d35Cc...");
```

## Type Definition

```typescript theme={null}
import type { AddressType } from '../Address/AddressType.js';
import type { brand } from '../../brand.js';

export type PaymasterType = AddressType & { readonly [brand]: "Paymaster" };
```

## API Reference

### from

Create Paymaster from address input.

```typescript theme={null}
function from(
  value: number | bigint | string | Uint8Array | AddressType
): PaymasterType
```

### toHex

Convert Paymaster to hex string.

```typescript theme={null}
function toHex(
  paymaster: number | bigint | string | Uint8Array | AddressType
): string
```

### equals

Check if two Paymaster addresses are equal.

```typescript theme={null}
function equals(
  paymaster1: number | bigint | string | Uint8Array | AddressType,
  paymaster2: number | bigint | string | Uint8Array | AddressType
): boolean
```

## Paymaster Functionality

Paymasters enable:

1. **Gasless transactions**: Sponsor user gas fees completely
2. **Token payment**: Users pay gas in ERC-20 tokens
3. **Conditional sponsorship**: Rules-based gas sponsorship
4. **Rate limiting**: Control spending per account/time period

## Usage with User Operations

```typescript theme={null}
import { UserOperation } from '@tevm/voltaire/primitives/UserOperation';
import { Paymaster } from '@tevm/voltaire/primitives/Paymaster';

const paymasterAddr = Paymaster.from("0x742d35Cc6634C0532925a3b844Bc9e7595f251e3");

// paymasterAndData format: paymaster (20 bytes) + paymasterData (variable)
const paymasterAndData = new Uint8Array([
  ...paymasterAddr,
  // ...paymasterData (paymaster-specific data)
]);

const userOp = UserOperation.from({
  sender: "0x...",
  nonce: 0n,
  // ... other fields
  paymasterAndData,
  signature: "0x",
});
```

## Related Types

* [Paymaster (Effect)](https://voltaire-effect.tevm.sh/primitives/paymaster) - Effect.ts integration with Schema validation
* [UserOperation](/primitives/user-operation) - User operation with paymaster field
* [EntryPoint](/primitives/entry-point) - Entry point contract
* [Bundler](/primitives/bundler) - Bundler address
* [Address](/primitives/address) - Base address type

## References

* [ERC-4337 Specification](https://eips.ethereum.org/EIPS/eip-4337)
* [Paymaster Contracts](https://github.com/eth-infinitism/account-abstraction/tree/develop/contracts/samples)