What is gamma exposure (GEX)?

The measurement behind every chart on this site

When you buy an option, someone — usually a market maker — sold it to you. That dealer does not want a directional bet; they want the spread. So they hedge: they hold enough of the underlying to offset the option's delta, and they adjust that hedge as the market moves. Gamma is the rate at which the option's delta changes, which means it is also the rate at which the dealer's hedge must change.

Gamma exposure (GEX) aggregates that obligation across every strike and expiry on the board. It answers one question: for a given move in the index, how much buying or selling do dealers as a group have to do, mechanically, to stay hedged?

Why the sign matters

When dealers are long gamma (customers net sold them options), their hedging leans against the market: they sell into rallies and buy into dips. That flow dampens moves — the market feels pinned, ranges compress. When dealers are short gamma (customers net own the options), hedging works the other way: they buy strength and sell weakness, adding fuel to whatever the market was already doing. Same tape, opposite feedback loop.

The price where the aggregate position crosses from one regime to the other is the zero-gamma flip. Where the biggest concentrations of dealer gamma sit defines the call resistance and put support levels.

How this site measures it

gex.live reconstructs dealer positioning for SPX from the 0DTE options tape — trade by trade, classifying each print's likely initiator and accumulating the dealer-side greeks minute by minute through the session. It is a measurement with error bars, not an oracle: open interest is not observable intraday, initiator classification is probabilistic, and the models are approximations. That is why the terminal shows vanna and charm alongside gamma, and why it deliberately shows no buy or sell arrows anywhere.

See it on real sessions

Every historical session is free to replay — the flip, the walls and the hedging pressure, minute by minute, on the days they mattered. If the chart itself is the unfamiliar part, read how to read a GEX chart first. Nothing on this page or any other is investment advice; see the Terms.