Aave is a DeFi Liquidity Protocol for Supplying and Borrowing

Do not read the displayed APY as a fixed promise

The displayed supply APY is a live estimate, not a fixed return. Treating it like a locked savings rate is the first common mistake because every reserve responds to borrowing demand, repayments, new deposits, and withdrawals.

Utilization measures the share of supplied liquidity that borrowers have drawn. V3 rate strategies use two slopes separated by one optimal-utilization point, commonly called the kink. Rates climb more sharply after utilization passes that point, encouraging repayment and additional supply. Incentive rewards, when present, are separate from the underlying supply rate and have their own budgets. Compare the reserve's utilization, available liquidity, cap, and collateral status before interpreting its APY.

Aave pools beside Compound III, Morpho Blue, and SparkLend

Aave pools combine several supplied and borrowed assets within governed liquidity markets. That structure differs from Compound III, where each Comet market has one borrowable base asset, and from Morpho Blue, where an isolated market is identified by five immutable parameters: loan token, collateral token, oracle, interest-rate model, and liquidation loan-to-value ratio.

As a rule, Aave's pooled structure emphasizes shared liquidity, broad collateral selection, and account-level health calculations. Morpho Vaults add curated allocation across isolated markets, while SparkLend applies a V3-derived pooled design within the Sky ecosystem. Compound III offers a narrower base-asset model. The meaningful choice is therefore market architecture: pooled multi-asset borrowing, isolated pair exposure, or curated vault allocation.

Supplying assets creates liquidity and an onchain claim

A supply position transfers a supported asset into a reserve and returns an interest-bearing aToken to the wallet. The contract issues aTokens at a 1:1 accounting ratio when assets enter, so aUSDC represents supplied USDC and aWETH represents supplied WETH. Interest appears through the liquidity index, which increases the redeemable aToken balance without requiring a separate claim transaction.

An eligible supply position also serves as collateral when collateral usage is enabled. This supports two primary uses: earning the variable supply rate and retaining the option to borrow without selling the supplied asset. Withdrawal burns the corresponding aTokens and returns the underlying asset, but only unborrowed liquidity is immediately available. A collateralized withdrawal must also leave the account within its borrowing limits.

Borrowing unlocks liquidity without selling collateral

A borrow position transfers an asset such as USDC or GHO to the borrower while recording variable debt onchain. The collateral remains supplied, interest starts accruing on the debt immediately, and the position stays open until it is repaid or becomes eligible for liquidation. Loan-to-value limits determine initial borrowing power; the higher liquidation threshold determines when collateral coverage has become insufficient.

Worked example with hypothetical inputs

Every changing input in this calculation is hypothetical: collateral value of $10,000, weighted liquidation threshold of 80%, borrowed USDC value of $5,000, annualized variable rate of 6%, elapsed time of 30 days, unchanged prices and rate, and no network fee. The starting health factor is $10,000 × 80% ÷ $5,000, or 1.60. A simple 365-day estimate adds $24.66 of interest, producing $5,024.66 of debt and a revised health factor of about 1.59.

Match the wallet, network, reserve, and gas asset

The first supply begins by matching a wallet to the exact blockchain deployment and reserve. Each Aave deployment has independent liquidity and contract addresses: Ethereum uses chain ID 1, Arbitrum One uses 42161, Base uses 8453, Polygon PoS uses 137, and Avalanche C-Chain uses 43114. MetaMask, Rabby, and Coinbase Wallet support EVM transactions, while the wallet also needs the network's native gas asset.

The same ground is broken down in Aave walkthrough. The entry path is short: select the network, choose a listed reserve, review its cap and collateral settings, then authorize and submit the supply. A conventional ERC-20 flow takes two onchain transactions - one allowance approval and one supply call. Where the asset and interface support approval by signature, the approval becomes one signed message and only the supply call consumes gas. Withdrawing the same wrapped underlying normally takes one onchain transaction and needs no new token approval.

Health factor sets the boundary for collateral risk

The health factor measures the collateral coverage of a borrow position. It divides collateral value multiplied by the weighted liquidation threshold by total debt value. Collateral price declines, borrowed-asset appreciation, and accrued interest all push the figure downward, while repayment or additional collateral moves it upward.

On Aave V3, a borrow position becomes eligible for liquidation when its health factor falls below 1. For a qualifying position above 0.95, up to 50% of total debt is liquidatable when both collateral and debt are worth at least $2,000. The close factor rises to 100% at 0.95 or below, or when either side is below $2,000. A partial liquidation must leave at least $1,000 of both collateral and debt; otherwise the position is cleared fully.

Chainlink price feeds supply the reference values used by supported EVM markets, while governance assigns each asset's loan-to-value ratio, liquidation threshold, bonus, and caps. Suppliers also carry reserve-liquidity risk: heavy utilization restricts immediate withdrawals even when the displayed aToken balance remains intact. Smart-contract, oracle, network, and underlying-token risk remain separate from the borrower's health factor.

Interest and transaction costs come from different mechanisms

A reserve's interest-rate model prices borrowing demand, while the blockchain prices transaction execution. An ordinary Aave V3 borrow has a 0% origination fee, but variable interest accrues per second. Suppliers receive the borrower-funded interest allocated through utilization and the reserve factor; part of the interest flows to the protocol treasury. The resulting APY changes whenever utilization or governance-set curve parameters change.

Gas is paid separately for approvals, supplies, borrows, repayments, and withdrawals. Its monetary cost combines at least two changing inputs: gas consumed and the network's unit price. Ethereum rollups such as Arbitrum and Base also incorporate data-posting costs. A small position can therefore have sound lending economics yet remain inefficient if several transactions consume a large share of the intended return.

aTokens, debt indices, Hubs, and Spokes under the hood

An aToken is an ERC-20-compatible representation of a supplied balance, while variable-debt accounting records what a borrower owes. V3 calculates an aToken balance from a scaled balance and liquidity index; variable debt uses a scaled debt balance and borrow index. The core math library defines WAD precision as 10 ¹⁸ , RAY precision as 10 ²⁷ , and the conversion ratio between them as 10 ⁹ .

Notably, Aave V3 organizes reserves inside a Pool deployment, with configuration contracts controlling asset parameters. V4 separates liquidity Hubs from market Spokes: a Hub accounts for shared liquidity, while Spokes define specialized borrowing and collateral rules. Both architectures preserve the central relationship between suppliers, borrowers, indices, caps, and oracle-priced collateral, although a position remains specific to its version, market, and network.

Flash loans, E-Mode, Isolation Mode, and GHO serve different jobs

Flash loans, E-Mode, Isolation Mode, and GHO extend the supply-and-borrow model in four distinct directions. They are protocol mechanisms rather than interchangeable yield features.

• Flash loans: Borrowed liquidity and the premium must return within one atomic transaction, or the entire transaction reverts.
• E-Mode: One selected category applies specialized collateral parameters and restricts borrowing to eligible assets in that category.
• Isolation Mode: One isolated collateral position borrows only governance-approved stablecoins and remains subject to its debt ceiling.
• GHO: The dollar-referenced stablecoin is minted and burned through governance-approved facilitators with defined bucket capacities.

The Ethereum V3 configuration sets the flash-loan premium at 5 basis points, or 0.05%. Four basis points go to the protocol treasury and 1 basis point goes to suppliers, although approved flash borrowers receive a waiver. GHO facilitators use separate issuance strategies, and Chainlink CCIP supports GHO movement between approved networks. These mechanisms introduce additional parameters beyond an ordinary supply position.

Governance and the AAVE token shape the next decision

In the same way, AAVE is the governance token used to vote directly or delegate voting power over protocol changes. Its designed maximum supply is 16 million tokens, and the earlier LEND migration used a fixed ratio of 100 LEND to 1 AAVE. Governance configures listings, caps, rate strategies, collateral rules, upgrades, and treasury actions; holding the token is separate from supplying or borrowing.

Umbrella replaced the legacy Safety Module as the protocol's newer deficit-coverage system, accepting supported aTokens or GHO for staking with defined slashing exposure. Before opening a position, settle four choices: the network, reserve, intended action, and acceptable collateral buffer. The strongest fit combines useful liquidity with manageable gas and a health factor that remains resilient when prices and interest move.