APY (annual percentage yield) is a projected yearly return that assumes rewards are compounded over the year. It looks larger than a simple annual rate because it bakes in reinvestment. In crypto dashboards, the number is often a snapshot of current incentives, not a locked bank coupon.
Why it matters
DeFi and exchange earn pages compete on APY screenshots. Those figures can include token emissions whose price falls as soon as farmers sell, temporary liquidity-mining boosts, or leveraged looping that multiplies both yield and liquidation risk. A calm reader asks where the yield comes from before treating the percentage as income.
APY also hides path dependency. If rewards are paid in a volatile governance token, your dollar return depends on that token’s price path, not only on the headline rate. If the protocol cuts emissions next epoch, yesterday’s three-digit APY becomes a museum piece.
Compare APY with APR carefully. APR usually excludes compounding. Neither metric proves solvency, oracle quality, or withdrawal liquidity. Yield is compensation for risk until proven otherwise.
Base yield from trading fees or borrower interest is usually more durable than emission APY, but it is still not risk-free. Utilization spikes, bad debt, and oracle failures can erase months of compounding in a day. When a venue shows a blended APY, split it into fee yield versus reward yield. If reward yield is most of the number, your return path depends on someone else buying the reward token after you. That is a market call wearing a savings label.
Display conventions differ by venue. Some screens annualize a one-day reward rate. Others blend borrowing interest paid by users with token incentives paid by a treasury. If you cannot rebuild the number from fee APY plus reward APY with transparent formulas, treat the headline as advertising. Write your own estimate with conservative reward prices and a short incentive half-life before you deposit size that would hurt to unlock slowly.
Example
A pool shows 180% APY funded mostly by a reward token. You model the same pool with reward price down 50% and emissions halved. The effective dollar yield collapses even if the interface still looks busy. Related: DeFi, TVL, and liquidation.