0DTE: the options that expire same day, and why they move you too
Hi trader,
in the first piece of this series I left you with a promise. I told you that the clean picture of GEX, the gamma flip, the call wall, the put wall, has become a lot shakier in recent years. And that the culprit is a new little beast: the options that expire same day, the 0DTEs.
Today I keep the promise.
But first, an honest heads-up. Here I’m assuming you already know what gamma and delta hedging are, meaning the market maker forced to buy and sell the underlying to stay neutral. If those sound new, don’t start here, stop and read the other piece first, otherwise we’ll just make a mess:
The first article: GEX, why some days the index sits still and others it collapses
Done? Good, vamos.
What they are, and why they exploded
0DTE stands for “zero days to expiration”. They’re options that are born and die within the same session.
Until a few years ago options expired on Friday, or once a month. Then on the S&P 500, the most heavily traded index in the world for options, they added expirations on every day of the week. That’s where the boom started.
Today 0DTEs have become a huge slice of the daily options volume on the index, on some days almost half of everything. It’s no longer niche stuff for a handful of tinkerers. It’s become a central part of how the market moves intraday.
And that’s exactly why they matter to you even if you wouldn’t touch an option with a ten-foot pole.
Why a few-hours expiration is a whole different animal
An option with weeks ahead of it behaves one way. The same option with only a few hours left behaves in a completely different way. There are three reasons.
Gamma turns enormous and concentrated. The closer expiration gets, the more the gamma of an option near the current price spikes. Near expiration, an option just below the price is worth almost nothing, just above it’s worth a fortune, and the switch between those two worlds is a blade. That forces market makers into violent, lightning-fast hedging around a handful of precise strikes.
Theta burns. Theta is time eating away at the option’s value. In a 0DTE the time left is ridiculous, and that value evaporates hour after hour like fuel from a punctured tank. By the close it has to be worth zero or everything, there’s no middle ground.
Delta flips from 0 to 1 fast. With weeks to go, an option’s exposure changes smoothly. A few hours from expiration it changes all at once: price crosses the strike and the option goes from counting for nothing to counting like a full position. It’s a switch, not a dial.
Put them together: monster gamma, time evaporating, exposure snapping. You’ve got a spring loaded onto a few levels, and it all releases before the bell.
What it does to the market
And here’s the effect you see on the chart, even without ever opening an options chain in your life.
Gamma piles up and resets in the same session. In the morning a mountain of gamma builds up around certain strikes. By evening that mountain has to disappear, because those options expire. The landscape you had at 10 isn’t the one you have at 4.
Pinning. When a lot of options pile up on one strike, market maker hedging tends to “nail” the price around it, like a magnet. The market circles that number and struggles to get away. It’s the barnacle-on-the-rock kind of day, but a surgical version, stuck to one precise strike.
In practice
The future spends the morning orbiting a level, say a big round clean number. Up twenty points, back. Down twenty, back. It looks magnetized. Often it’s exactly a strike loaded with 0DTEs acting as a magnet, with market makers hedging their books keeping it there.
End-of-day moves. As the close gets closer and gamma unwinds, that magnet can let go all at once. And there you have the last-hour bursts, the market that sat still all day and then takes off like a slingshot in the final thirty minutes.
How it changes the way you read GEX
Does the hook from the first article come back to you? Here it is.
When a big chunk of the open interest expires same day, the GEX map becomes unstable intraday. The gamma flip, the call wall and the put wall you calculate at the open can shift by the afternoon, because part of that gamma is alive for today only and evaporates tonight.
Put simply: the read on the regime is still very useful, but it’s no longer a snapshot good for the whole day. It’s a video, changing while you watch it. It has to be refreshed, not printed in the morning and pinned to the wall.
It’s also why having your levels updated, instead of recalculating them by hand, isn’t a luxury. On Thunder Desk you’ll find the gamma exposure on S&P and Nasdaq updated, free, so you can see whether and how the map has moved without having to comb through the options chain every couple of hours.
What it means if you trade the underlying directional
Okay, but maybe you don’t touch options, you trade futures or CFDs on the index. Why should you care?
Because the pinning and the closing bursts show up on the very chart you trade.
Three concrete things:
- if price is orbiting a level and going nowhere, before you push the breakout ask yourself whether it’s a 0DTE magnet. In that case the breakout is almost always a false signal until the magnet lets go
- the last hour and a half can change the face of the day. A flat session can accelerate hard into the close when gamma unwinds
- round, “loaded” levels act as a magnet while they hold, and as a springboard once they give way
It’s not an entry signal, I’ll repeat the point from the first piece: it’s context. But it’s context that explains why on some days your breakout dies and on others the market runs away from you at half past four.
The real risks, for anyone who trades them
Now let’s talk to whoever feels the temptation to sell them, because “they expire today anyway, I pocket the premium and go home”. Hold on a second.
Assignment, but with an important technical clarification. Options on the S&P 500 index (SPX) are European style and cash settled: you don’t get anything delivered to you and there’s no early exercise. But options on ETFs and single stocks, the American ones, yes: there the assignment risk is real, and on a 0DTE that closes just in the money it can land on you when you least expect it. Knowing which instrument you’re selling is not a detail.
Spread and slippage. In fast phases spreads widen and filling an order at the price you wanted becomes an illusion. On a few-hours expiration, where everything races, this eats a slice of your edge before you even start.
Asymmetry, the number one risk. When you sell an option you collect a small, defined premium. But if the market moves against you fast, and with 0DTE gamma it moves against you fast indeed, the loss can be much, much bigger than the premium you collected. You’re picking up coins in front of a steamroller. Ninety-five times you pick them up. The hundredth time you don’t get out of the way.
I’m not telling you this to scare you, I’m telling you because it’s the part the dream-sellers on social never mention.
Do they really make the market more fragile?
There’s a serious debate on this, and I want to give it to you straight, no cheerleading.
On one side there are those who say 0DTEs are fuel: all this concentrated gamma unwinding within the day can amplify intraday moves, create little cliffs when the hedges all fire at once. The fear of an avalanche effect crammed into a few hours.
On the other side there are those who play it down: they say buyers and sellers are more or less balanced, that the net gamma in market makers’ hands is smaller than it looks, and that so far, despite the enormous volumes, no real systemic disaster has shown up. Intraday stuff, that closes out by the end of the day.
The honest truth is that there’s no settled answer yet. They’re a young instrument for how big they’ve gotten so fast. What we can say with both feet on the ground is that they’ve made the intraday more nervous and more technical, and that ignoring them today is like driving while pretending the other people on the road aren’t there.
Three things to take home
- 0DTEs concentrate enormous gamma on a few strikes that’s born and dies within the day: hence the pinning toward loaded strikes and the end-of-session bursts.
- They make the GEX map unstable intraday: it stays useful, but it has to be updated during the day, not photographed in the morning.
- If you sell them, the number one risk is the asymmetry between the small premium you collect and the loss that can turn enormous. The coins in front of the steamroller.
And here I close the circle. If you missed the first piece, or you want to reread where all this talk about gamma and market makers comes from, it’s here:
Back to the first article: GEX explained simply
If instead you want to put order in your method before you slip into these dynamics, start from the free ebook Win the Arena, and keep the Desk open while you trade. The Events on The Thunder Trader are on forex, CFDs and crypto in a demo environment, but the ability to read the underlying’s regime you carry with you to any market. It’s a competitive edge, not a nerd detail.
That’s me, done. If you’ve got a friend who sells zero-expiration options “because it’s easy money”, send him this piece. At coin number one hundred he’ll thank you.
Suerte Amigo!
Tiziano Brunno
Tradingblog
Disclaimer: purely informational and educational content. It does not constitute financial advice nor an invitation to trade. Trading carries the risk of capital loss. Selling options carries a risk potentially far greater than the premium collected and is not suitable for most operators: inform yourself thoroughly and evaluate carefully before trading.
