This is a live gamma exposure chart for S&P 500 index options. It plots dealer gamma exposure (GEX) strike by strike against SPX price, so you can see where options market makers are forced to hedge — and where that hedging tends to turn into support and resistance.
Gamma exposure measures how much the dealer community's aggregate delta changes as SPX moves. Because dealers hedge to stay delta-neutral, a large gamma position at a given strike translates into mechanical buying or selling as price approaches it. That flow is not a prediction; it is a structural pressure that exists regardless of anyone's opinion on direction. Gamma Exposure (GEX) explained →
Three levels do most of the work on this chart:
Walls are not guarantees. They mark where hedging flow is densest, which means they are where moves most often stall, pin, or accelerate once broken. Why SPX pins at certain strikes →
The single most useful number on the panel is net GEX — the sum of dealer gamma across all strikes, expressed in dollars per 1% move.
When net SPX GEX is positive, dealers are long gamma. They sell rallies and buy dips to stay hedged, which suppresses realised volatility. Ranges compress, moves mean-revert, and price tends to gravitate toward high-gamma strikes into the close.
When net SPX GEX is negative, the sign flips. Dealers now buy strength and sell weakness, amplifying whatever the market is already doing. Ranges expand, trends persist longer than they "should", and air pockets open up between strikes. Most outsized SPX sessions happen below zero gamma. Positive vs negative gamma →
For each strike, gamma exposure is the contract's gamma multiplied by open interest, the contract multiplier, and spot squared, scaled to a 1% move. Those per-strike values are then signed according to an assumption about which side of the book dealers sit on — conventionally long calls and short puts — and summed into the net figure.
That signing convention is an assumption, not an observation, and it is the single largest source of error in any public GEX model. We are explicit about where ours can be wrong, and about which approaches we tested against each other. Full GEX methodology and assumptions →
Same-day expiry options now account for roughly 60% of SPX options volume. Because gamma is at its most violent in the final hours before expiry, a large share of the market's total gamma is concentrated in contracts that will not exist tomorrow.
The practical consequence is that SPX gamma levels decay intraday in a way they simply did not a decade ago. A Call Wall that is pinning price at 11am can be irrelevant by 3pm as that day's open interest burns off. This is why the chart separates 0DTE from the full expiry stack. How 0DTE options move SPX →
Yes. The SPX gamma levels, the chart, and the net GEX reading are free to use. A Pro tier adds real-time updates, alerting, and VIX fair value tooling.
Levels are recalculated through the session as new open interest and price data arrive. The panel shows a countdown to the next scheduled GEX update.
No, and treating it that way is the most common mistake. GEX describes the hedging pressure dealers are under at each price. It tells you how the market is likely to behave — pinning versus trending, compressing versus expanding — not which way it will go.
They are related but not interchangeable. SPX and SPY track the same index, but each has its own options chain, its own open interest, and its own dealer positioning, so SPY GEX is not simply SPX GEX divided by ten. SPX carries the larger notional and the bulk of institutional 0DTE flow, which is why these levels are built from the SPX chain.
OPRA and OCC open interest, with dealer-flow context from FINRA ATS and DTCC data. What FINRA ATS and DTCC data actually reveal →
More on dealer positioning: Dealer Flow · Market Maker Hedging · Gamma Squeeze · Vanna & Charm Flows · OPEX Effect · Dark Pools · VIX Fair Value