Flash Loans

Overview

The Vault holds tokens for all pools in a single contract making the consolidated token balances available for flash loans. On mainnet the vault holds over a billion dollars worth of assets. Currently there are 0 fees for flash loans.

These features make Balancer one of the most prominent sources for flash loans in defi.

Example Code

pragma solidity ^0.7.0;
 
import "@balancer-labs/v2-interfaces/contracts/vault/IVault.sol";
import "@balancer-labs/v2-interfaces/contracts/vault/IFlashLoanRecipient.sol";
 
contract FlashLoanRecipient is IFlashLoanRecipient {
    IVault private constant vault = "0xBA12222222228d8Ba445958a75a0704d566BF2C8";
 
    function makeFlashLoan(
        IERC20[] memory tokens,
        uint256[] memory amounts,
        bytes memory userData
    ) external {
      vault.flashLoan(this, tokens, amounts, userData);
    }
 
    function receiveFlashLoan(
        IERC20[] memory tokens,
        uint256[] memory amounts,
        uint256[] memory feeAmounts,
        bytes memory userData
    ) external override {
        require(msg.sender == vault);
        ...
    }
}

Error Codes Internal User Balances