Option contracts that expire in the same day's session. Their time value is almost zero, so they move violently on any price change. Dealer hedging of these contracts does the most to amplify index moves within the session.
What these contracts are
0DTE (0DTE · Zero Days To Expiration) contracts are options on their last day: opened in the morning, settled in the evening. They have become the defining trade of the moment, with about half of the volume in the major index options, now that daily expirations exist on the main indexes.
Extreme mechanics
All the contract's features are squeezed into a few hours: Theta eats all the time value before the bell, and Gamma is at its fiercest. For an At the Money contract, delta jumps from 0.5 toward 1 or 0 on a small move. That is huge leverage in both directions, so the contract can double or vanish within minutes.
Its effect on the market itself
Their huge volumes create dense, instant hedging by dealers: gamma walls form and dissolve within a single session, producing sharp pulls and bounces (strongest in the last two hours). Reading the one-day gamma map has become an analysis layer of its own for intraday index traders.
Hypothetical example
A calm index in the morning approaches a daily call wall at 6000 at noon. Opposite hedging holds the approach back twice, then a high-volume break after a data release turns that hedging into fuel. The index runs twenty points in a quarter of an hour. The daily structure created the whole scenario without one piece of company news.
Common mistake
Treating them as a small investment is the mistake. They are pure timing tools whose time value burns by the hour. Whoever waits for them to recover is waiting in a building that is demolished by evening. Size the risk assuming they go to zero, not hoping to sell.
Where to see it on the platform
The gamma board covers the daily-expiration structure in the index map, and the education pages explain the risks with examples.
