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

# EIP-4337

> How ERC-4337 account abstraction works on Polygon PoS, including UserOperations, Bundlers, EntryPoints, and Paymasters.

The ERC-4337 standard, also known as EIP-4337, allows developers to achieve account abstraction on the Polygon PoS. This page provides a simplified overview of the different components of ERC-4337 and how they work together.

The ERC-4337 standard consists of four main components: `UserOperation`, `Bundler`, `EntryPoint`, and `Contract Account`. Optional components include `Paymasters` and `Aggregators`.

## Building ERC-4337 transactions

ERC-4337 transactions are called `UserOperations` to avoid confusion with the regular transaction type. `UserOperations` are pseudo-transaction objects that are used to execute transactions with contract accounts. ERC-4337 transactions have to be sent to nodes that include ERC-4337 bundlers.

The `UserOperation` object has a few fields.

| Field                  | Type      | Description                                                                             |
| ---------------------- | --------- | --------------------------------------------------------------------------------------- |
| `sender`               | `address` | The address of the smart contract account                                               |
| `nonce`                | `uint256` | Anti-replay protection                                                                  |
| `initCode`             | `bytes`   | Code used to deploy the account if not yet onchain                                      |
| `callData`             | `bytes`   | Data that's passed to the `sender` for execution                                        |
| `callGasLimit`         | `uint256` | Gas limit for execution phase                                                           |
| `verificationGasLimit` | `uint256` | Gas limit for verification phase                                                        |
| `preVerificationGas`   | `uint256` | Gas to compensate the bundler                                                           |
| `maxFeePerGas`         | `uint256` | Similar to EIP-1559 max fee                                                             |
| `maxPriorityFeePerGas` | `uint256` | Similar to EIP-1559 priority fee                                                        |
| `paymasterAndData`     | `bytes`   | `Paymaster Contract` address and any extra data required for verification and execution |
| `signature`            | `bytes`   | Used to validate a `UserOperation` along with the `nonce` during verification           |

## ERC-4337 wallets

Users must have an ERC-4337 smart contract account to validate `UserOperations`. The core interface for an ERC-4337 wallet is:

```solidity theme={null}
interface IAccount {
  function validateUserOp
      (UserOperation calldata userOp, bytes32 userOpHash, address aggregator, uint256 missingAccountFunds)
      external returns (uint256 sigTimeRange);
}
```

## Resources

* [ERC-4337 proposal](https://eips.ethereum.org/EIPS/eip-4337) is the link to the official proposal and technical specification.
* [@account-abstraction SDK](https://www.npmjs.com/package/@account-abstraction/sdk) is an npm package for using ERC-4337 developed by the authors of the proposal.
* [Stackup](https://docs.stackup.sh/) provides node services with ERC-4337 bundlers and other ERC-4337 infrastructure.
* [WalletKit](https://walletkit.com) is an all-in-one platform for adding smart, gasless wallets to your app. It has integrated support for ERC-4337 and comes with a paymaster and bundler included, requiring no extra setup.