Why 0DTE Options Changed Market Structure
Zero-day-to-expiration options (0DTE) now routinely account for more than 40% of total SPX options volume on normal sessions and over 50% on event days. That headline number understates how deeply daily expirations have reshaped US equity index market structure since the CBOE completed the SPX Monday–Friday expiration cycle in 2022.
The dominant feature of intraday SPX and SPY price action is no longer discretionary trader sentiment, news flow, or macro data in isolation. It is the gamma profile of the options chain that expires today, and the mechanical hedging of that profile by dealers. This intraday gamma engine pins, accelerates, and repeatedly resets the tape on a clock that ends at 4:00 PM ET.
This article explains what changed, why it changed, and how to read modern market structure through the 0DTE lens.
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What 0DTE actually is
0DTE refers to options that expire at the close of the current trading session.
- In May 2022, the CBOE introduced daily SPX expirations, completing the rotation that had previously included only Monday, Wednesday, and Friday.
- Daily expirations on QQQ followed.
This opened the door to a trading style that previously did not exist at scale: systematically buying or selling options with hours to expiry instead of days or weeks.
Within a year:
- 0DTE volume reached ~40% of SPX options flow.
- By 2024, it routinely exceeded that on event days.
Participants include:
- Retail traders seeking leveraged intraday exposure.
- Systematic dealers and prop firms running short-gamma and intraday volatility strategies.
- Institutional desks increasingly using 0DTE for tactical hedging around data releases, Fed days, and large flows.
The key definitional point:
At the close, a 0DTE option has zero time value. As expiry approaches, its gamma collapses into a sharp spike at the strike.
That gamma collapse is the engine behind the structural changes discussed below.
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Why gamma concentrates so violently at 0DTE
Gamma is the rate of change of an option’s delta with respect to the underlying price.
- For long-dated options, gamma is relatively small and spread across a wide range of strikes. Delta changes gradually as the underlying moves.
- For short-dated options, gamma is larger and concentrated near the at-the-money (ATM) strike. Delta changes quickly with small price moves.
- For an ATM option in its final hour, gamma can be enormous: a tiny move in the underlying can flip delta from ~0.5 toward 1 (deep ITM) or toward 0 (deep OTM).
Dealer hedging implication:
- A dealer net short the ATM 0DTE strike must dynamically hedge with the underlying.
- As spot drifts a few points, the option’s delta can change dramatically.
- The dealer’s hedge size must adjust mechanically and quickly, often in size large enough relative to the order book that the hedging itself moves the underlying.
In longer-dated markets, dealer hedging is a steady current.
In 0DTE markets, dealer hedging is a breaking wave that interacts with the order book minute by minute.