ERC-3156 (erc3156)

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What it offers

• flashFee: Query the fee for a flash loan of a specific token and amount
• maxFlashLoan: Query the maximum flash loan amount for a token
• flashLoan: Execute a flash loan (borrow and repay in same transaction)

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Notes

• Standard interface (EIP-3156), not a specific deployment - no fixed addresses
• Conforming lenders implement all three functions: Maker’s DssFlash (DAI) and Aave’s GHO flash minter (GHO), for example, or an ERC-3156 adapter in front of another protocol’s flash loans. maxFlashLoan(token) is non-zero for a token the lender lends
• Protocol-specific flash loans are not ERC-3156, and flashFee/maxFlashLoan revert there: Aave V3’s Pool (flashLoanSimple/flashLoan, receiver callback executeOperation, premium FLASHLOAN_PREMIUM_TOTAL in basis points), Balancer V2’s Vault (flashLoan(recipient, tokens, amounts, userData), callback receiveFlashLoan) and Uniswap V3 pools (flash, callback uniswapV3FlashCallback). Call those through their own protocol’s interface
• Receiver contract must implement onFlashLoan(address,address,uint256,uint256,bytes) callback
• Must approve lender to pull back amount + fee before callback returns
• Flash loan must be fully repaid within the same transaction (atomic)
• The fee is each lender’s: read it with flashFee(token, amount) before borrowing

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Its names in a program

import FlashLenderABI from "./protocols/erc3156/FlashLenderABI.json";

// The contract's address, a `main` argument.
function main(contract: Address) {
  const target = FlashLenderABI.at(contract);
}

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ABI

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FlashLenderABI

• flashLoan(address receiver, address token, uint256 amount, bytes data) returns (bool)
• flashFee(address token, uint256 amount) view returns (uint256)
• maxFlashLoan(address token) view returns (uint256)

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Next steps

• Protocols: the other protocols, by what they do.
• Protocols and tokens: calling a contract by its namespace, or through its ABI.
• Glossary: the words these pages use, in plain terms.