Learn SPX dealer positioning: GEX, the flip, walls, vanna, charm
The concepts behind the terminal, in plain language
FirmTape reconstructs SPX options dealer positioning from the tape and shows it as it moves. These pages explain what the measurements mean — and just as deliberately, what they do not mean. None of it is investment advice.
What is gamma exposure (GEX)?
Gamma exposure (GEX): how much dealers buy or sell to stay hedged as SPX moves — and why that hedging dampens or amplifies volatility.
The zero-gamma flip line, explained
The zero-gamma flip: the index level where dealers' net gamma changes sign: above it hedging dampens volatility, below it it amplifies moves.
Call resistance and put support
Call walls and put support are the strikes carrying the heaviest dealer gamma, levels where hedging flow concentrates and price often stalls or pins.
Vanna and charm: the second-order flows
Vanna and charm are the second-order greeks behind systematic dealer flows: hedging triggered by implied-vol changes and by the pure passage of time.
How to read a gamma exposure (GEX) chart
How to read a GEX chart: the gamma ladder by strike, the flip line, call and put walls — and what a gamma exposure indicator can and cannot tell you.
How dealer hedging moves the market
What a market maker actually does after selling you an option, why that hedging is mechanical rather than discretionary, and how it becomes a measurable flow in SPX.
What are 0DTE options?
0DTE options explained: same-day-expiry SPX contracts, why their gamma is so large, how they changed intraday dealer positioning, and what the research actually shows.
What is a gamma squeeze?
How dealer hedging turns buying into more buying, the real mechanism behind a gamma squeeze, what it needs to happen, and why the index version is milder than the meme.
What is max pain, and does it work?
Max pain: the strike where the most options expire worthless. What the theory claims, and what 1,072 SPX sessions say about whether open interest actually pins the index.
Open interest vs volume in options
The difference between open interest and volume, why a dealer-positioning book built on one is not the same as one built on the other, and which the measurements favour.
Implied volatility skew explained
Why index puts price above calls, what the 25-delta risk reversal measures, and what 506 SPX sessions say about using a skew extreme as a reversal signal.