⏱️ 0DTE & GEX
0DTE — zero-days-to-expiration — options expire the same session they trade. On index names (SPX, SPY, QQQ, XSP) they now represent ~40–50% of daily options volume. Because gamma is largest for options near their strike and near expiration, 0DTE flows dominate intraday GEX on those tickers.
Why 0DTE gamma is so powerful
- Peak gamma at expiry.A contract's gamma function peaks when it's ATM and near expiration. 0DTE satisfies both at once.
- Small moves, big dealer hedges. A $0.50 move in SPY at a loaded 0DTE strike can force dealers to buy or sell tens of millions of delta within minutes.
- The board reshapes every day. 0DTE open interest vanishes at 4pm ET and the next session rebuilds from scratch.
What to watch on the heatmap
- The leftmost column of the GEX heatmap (nearest expiration) — on SPY/SPX it is the 0DTE column.
- Watch how the King Strike migrates through the session as 0DTE positioning shifts.
- Use the GEX Flow panel to quantify how 0DTE gamma built or drained since the open.
- Into the last 30–60 minutes, pinning is strongest if a strike has dominant call-and-put gamma stacked.
💡 : On 0DTE-heavy tickers, positive-gamma regimes compress realized volatility into the close; negative-gamma regimes produce the opposite — sharp late-day moves.
💡 0DTE is concentrated on index names. On single stocks, the weekly options cycle (and OpEx Friday) usually dominates instead — see OpEx Dynamics.
🔑 Key Takeaways
- 0DTE peaks gamma at the current price — tiny moves trigger big hedges.
- The leftmost heatmap column on SPY/SPX is usually 0DTE.
- Positive gamma into the close compresses the tape; negative gamma amplifies it.
- Use GEX Flow to see how 0DTE positioning evolved through the session.