⏱️ 0DTE & GEX
0DTE — zero-days-to-expiration — options expire the same session they trade. On index names (SPX, SPY, QQQ, XSP) they now make up a large share of daily options volume. Because gamma is largest for options near their strike and near expiration, 0DTE flows dominate intraday gamma exposure (GEX) on those tickers — often setting the magnets and walls that shape how price travels into the close.
This page explains why same-day expiries carry such outsized gamma, what to look for on the GEX heatmap, and how to isolate or exclude the 0DTE column so you can read the rest of the board cleanly.
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 0DTE column. The leftmost column of the GEX heatmap is the nearest expiration — on SPY/SPX that is the same-day (0DTE) column, and it often carries the heaviest gamma on the board.
- 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.
Isolating or excluding 0DTE#
Because same-day gamma can overwhelm everything else, GammaBaba lets you read the board both ways. Focus on the 0DTE column on its own to gauge intraday pinning pressure, or flip the Exclude-0DTE toggle to drop same-day expiries entirely and see the structural walls that persist into later sessions and OpEx.
- Keep 0DTE in. Best for last-hour pinning, intraday magnets, and reading where dealers are most reactive right now.
- Exclude 0DTE. Useful when same-day flow is masking durable call and put walls, or when you want a view that more closely resembles a single-stock board without daily expiries.
The Projection Heatmap overlays an expected price path on the same grid, so you can see how the King Strike and the surrounding gamma walls are likely to shepherd price — with or without the 0DTE column in play.
The risks#
- The board resets daily. 0DTE positioning that looks dominant at the open can drain within hours, so a read taken early may not hold into the afternoon.
- Gamma can flip fast. A move through a heavily loaded strike can swing a name from positive to negative gamma, turning a calm tape into a volatile one with little warning.
- Pinning is a tendency, not a guarantee. Macro catalysts and large directional flow can overpower even a strong gamma magnet.