Aave V3

Aave V3 is the dominant on-chain lending protocol. Users supply assets to earn yield and borrow against collateral. The protocol runs on Ethereum, Arbitrum, Optimism, Base, Polygon, and other EVM chains with identical interfaces. All interaction goes through the IPool contract.

What You Probably Got Wrong

LLMs confuse V2 and V3 constantly. V3 has different interfaces, different addresses, and different behavior. These corrections are non-negotiable.

• V3 is not V2 — different interfaces everywhere — V2 uses LendingPool with deposit(). V3 uses Pool with supply(). The function signatures, events, and return types differ. If you see ILendingPool or deposit(), you are writing V2 code. Stop.
• aTokens rebase — balance changes every block — aToken.balanceOf(user) increases each block as interest accrues. This is not a transfer. Do not try to track balances with Transfer events alone. Use balanceOf() at read time or scaledBalanceOf() for the underlying non-rebasing amount.
• Stable rate borrowing is deprecated on most markets — Aave governance disabled stable rate borrows on Ethereum mainnet and most L2 deployments. Use VARIABLE_RATE = 2 for the interestRateMode parameter. Passing STABLE_RATE = 1 will revert on markets where it is disabled.
• Health factor is 18-decimal fixed point, not a percentage — getUserAccountData() returns healthFactor as a uint256 with 18 decimals. A health factor of 1e18 means liquidation threshold. Below 1e18 = liquidatable. Do not divide by 100.
• Flash loan fee is 0.05% on V3, not 0.09% — V3 reduced the default flash loan premium from 0.09% (V2) to 0.05%. The exact fee is configurable per market via governance. Check FLASHLOAN_PREMIUM_TOTAL on the Pool contract.
• E-Mode changes collateral/borrow parameters — Enabling E-Mode (Efficiency Mode) overrides LTV, liquidation threshold, and liquidation bonus for assets in the same category (e.g., stablecoins). It does NOT change the underlying asset. Forgetting this causes incorrect health factor calculations.
• Supply caps exist in V3 — V3 introduced per-asset supply and borrow caps. supply() will revert if the cap is reached. Always check getReserveData() for supplyCap before large deposits.
• V3 addresses are different per chain AND per market — Ethereum has a "Main" market and a "Lido" market with completely different Pool addresses. Always verify you are targeting the correct market.

Quick Start