# Permit2 Overview (/docs/protocols/permit2/overview)

Learn how Uniswap Permit2 combines signature-based transfers and time-bound allowances for token spending.

[Permit2](https://github.com/Uniswap/permit2) is a unification of 2 contracts, `SignatureTransfer` and `AllowanceTransfer`. The `SignatureTransfer` contract handles all signature-based transfers, meaning that an allowance on the token is bypassed and permissions to the spender only last for the duration of the transaction that the one-time signature is spent. The `AllowanceTransfer` contract handles setting allowances on tokens, giving permissions to spenders on a specified amount for a specified duration of time. Any transfers that then happen through the `AllowanceTransfer` contract will only succeed if the proper permissions have been set.

## Resources
An external [explanation](https://github.com/dragonfly-xyz/useful-solidity-patterns/tree/main/patterns/permit2) of Permit2 contract patterns and example usage.

## Approving Permit2
Before integrating contracts can request users’ tokens through Permit2, users must approve the Permit2 contract through the specific token contract by calling something like:

```solidity
USDC.approve(permit2Address, totalAmount);
```

To maximize Permit2 utility, users can choose a max approval on the contract where:

```solidity
totalAmount = type(uint256).max;
```

## Where to Go Next
* Learn allowance flows in [Allowance Transfer](/docs/protocols/permit2/concepts/allowance-transfer)
* Learn signature flows in [Signature Transfer](/docs/protocols/permit2/concepts/signature-transfer)