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Why the Flexible APY Changes Every Day
The page showed one number when you deposited, and a few days later it's half that, with the money untouched. The platform didn't change the rules — the number was never fixed.
The one-line answer: the Flexible APY is the lending market's current quote. More borrowers and it rises; nobody borrowing and it falls. It moves constantly, and the number on the page only represents the moment you looked.
The money comes from the people borrowing
To understand the movement, first know who pays the interest. You put USDT into Flexible, the platform lends those coins to people who want them, the borrowers pay interest, the platform keeps a slice, and the rest is split among depositors.
Who borrows stablecoins? Mainly traders wanting leverage. They're bullish on some coin, don't have enough spot, and borrow USDT to buy. That loan costs interest, and they're willing to pay it, because in their arithmetic, the rally will exceed the interest.
Which gives you a very direct chain: hot market → more people wanting leverage → more demand to borrow USDT → borrowing rates rise → your Flexible APY rises with them. In reverse, when things are quiet and nobody wants to move, nobody borrows, and the APY falls away.
That also explains something a lot of people find counter-intuitive: stablecoin interest is highest when the market is at its most frenzied. Not because the platform is feeling generous then, but because that's when borrowers will pay up.
Three other things pushing it around
The platform's campaign budget
Limited-time boosts, new-user exclusives, new-money-only rates: these numbers don't come from the lending market, they come from the platform's customer acquisition budget. Easy to identify: there's a cap, there's a time window, and there's often a restriction on where the money came from. When the campaign ends the APY returns to the base level, which looks like it "halved out of nowhere" when really the campaign just expired.
Tiered design
The common wording is "the first X coins at the high rate, anything above that at the base rate". If you only deposited a small amount during a campaign, you got the high tier; add to it later and the excess only earns the base tier, dragging your blended APY down. It feels like "the APY dropped", but not a word of the rules on the page changed. We work that arithmetic separately in bonus APY versus base APY.
The wider rate environment
Stablecoin yields don't live in a vacuum. When risk-free rates in traditional markets are high, the cost of capital on-chain rises with them, and vice versa. This layer moves slowly, but it sets where the whole range is centred — that is, roughly what an APY looks like in the off-season.
So how should you read the number
Three practical readings.
One: treat it as a quote, not a promise. The APY on the page is the price right now, not your return over the next year. Deposit for thirty days and what you actually receive is the accumulation of each day's quote, which has little to do with the number you saw on the day you subscribed.
Two: compare ranges, not single points. To judge whether a platform's Flexible product is any good, look at its level in the quiet periods, not its campaign peaks. Everyone has a peak; the trough is where you find out.
Three: don't move house for a fraction of a percentage point. Before choosing between Flexible and Locked, work through the arithmetic in Locked pays a few points more: shuffling coins between platforms costs network fees and carries operational risk during the transfer. Turn the spread into an amount with the interest estimator and you'll probably find it doesn't cover the cost of the move.
The reverse warning: if a platform's Flexible APY is persistently well above its peers and it isn't a campaign, that excess has to come from somewhere. It may be deploying the money somewhere riskier, or it may be paying up to attract deposits. A stable high rate is a phenomenon that needs explaining, not a benefit you can simply enjoy.
When the APY suddenly changes
Knowing the mechanism lets you anticipate the typical moments, so you don't assume something has broken every time.
The days after a big move up or down
A violent market changes two things at once: the number of people wanting leverage, and the borrowing demand released by forced liquidations. Those two forces together often push rates to an unusual place for a few days afterwards, then it settles back. A high APY you see at such a moment probably won't last.
The day a campaign starts and the day it ends
A limited-time boost makes the number jump; the end of the campaign makes it jump back. Those two moments are the ones most likely to make people think the platform changed the rules. Easy check: look for a campaign tag or a date next to the number. If there's one, it's a campaign; if there isn't, that's the base level.
When your own position changes
The most misread of them all. Adding funds and exceeding the bonus cap, moving money from one product to another, or redeeming and re-subscribing and being classed as "not new money": all of these change the blended APY you see, with the platform doing nothing.
Quarter-ends and around holidays
Funding conditions often shift in patterned ways at these points, on-chain and off. The effect is usually small, but if you're planning short-term cash, knowing it exists saves some confusion.
What to do about it: most of the time, the right response is no response. Move the money because the APY fell and the number at the destination will often have moved before you arrive — while the cost of moving is certain. Only when a platform's level is persistently below its peers is switching worth serious thought.
Why we don't publish specific numbers
Writing this, we checked several public sources for stablecoin APYs, and they disagreed wildly: some said three or four percent, others said over ten. They aren't necessarily wrong; they're measured on different bases, at different moments, across different product types.
That's why we decided never to hard-code an APY anywhere on this site: any number copied down becomes wrong information on the page within days, and readers take it at face value and act on it. So we write rules and ranges with the date we checked, and leave the number itself to what Binance shows you at the time. The cost is that the page looks less "substantial"; the benefit is that it doesn't mislead.
When comparing platforms, what's worth comparing
If single-point numbers are meaningless, how do you judge whether a platform's Flexible product is good? Four comparable dimensions, ordered from easiest to hardest to verify.
Compare the quiet-period level. What each platform pays when nothing is happening reflects its real cost of funds and its willingness to share; everyone has a peak when things are busy. This one is the easiest to check: pick a week with no market news, screenshot the Flexible page of each platform you're watching, and do it again a month later. The difference between those two screenshots says more than any single day's number.
Compare the bonus tier caps. Two platforms both headline a high APY, but one covers the first few hundred coins and the other the first few thousand: a big difference in what it means to you. The arithmetic is in bonus APY versus base APY.
Compare how smoothly redemption works. You can't see this in a number; you have to test it once with a small amount. Put something in, redeem it the next day, and note how long it took from tapping confirm to the coins landing in Spot. A fraction of a percentage point is a paper matter; "how long until I have the money when I need it" is information you'll actually use.
Compare how much they're willing to tell you. A platform that spells out where the money goes, the redemption conditions and what happens in extreme situations is more reliable than one that just displays a big number.
Of those four, only the first has anything to do with the APY figure.
For the structural differences between these products, carry on to how the products differ structurally; for what actually happens to the money, see what the platform does with the coins you deposit.