Three free charts, three different flip levels
Searching for a free gamma exposure chart usually ends at whichever tool ranks first. Then you open a second one, and the zero-gamma level sits forty points away from the first. Neither site is broken, and neither is lying to you.
The reason is that a gamma exposure chart is not a measurement. It is a model output. Nobody publishes dealer inventory, so every GEX chart in existence — free or four figures a month — infers it from a set of assumptions. Free tools make those assumptions in different places, and they rarely put them on the same screen as the chart.
This is not a reason to avoid free charts. It is a reason to know which four things to check before you let one influence a trade.
What the chart is actually computing
The arithmetic most free charts run is simple: for every listed strike, multiply the option's gamma by its open interest by the contract multiplier by spot, sign calls positive and puts negative, and aggregate. The word doing the heavy lifting is the sign, because nobody publishes dealer inventory. Whether a strike counts as positive or negative gamma is a judgement about who is holding it, and that judgement is where free charts quietly diverge.
There are two ways to make it. The first is to assume it. SpotGamma states its assumption plainly on its free SPX gamma exposure page: options liquidity providers are treated as short puts and long calls, and the resulting chart is explicitly "not a forecast of direction." Calls positive, puts negative, applied uniformly. It is the convention the majority of free tools inherit.
The second is to infer it from the tape. The SqueezeMetrics research guide, from the firm whose research popularised the GEX acronym, does not apply a blanket sign at all. It builds Dealer Directional Open Interest by assessing the trade direction of option volume through the day and then comparing that volume against the subsequent change in open interest, and only then decides which side dealers ended up on. Its guide is explicit that a rise in open interest does not by itself imply dealers took on exposure. That is a materially different model, and it reports its output in thousands of dollars per index point rather than as a spot-scaled sum.
Same three letters, two different constructions. Neither is wrong, and a chart built either way is useful — but it is the first reason two free charts of the same session will not agree, and almost none of them say which one they did.
The sign convention is the foundation of the whole picture. If it holds, positive net gamma means dealers sell strength and buy weakness to stay hedged, which suppresses realised volatility; negative net gamma means they do the opposite and amplify it. That hedging loop is the mechanism the entire chart is a picture of.
Check one: how old is the open interest?
Open interest is a cleared, settled figure. It is the count of contracts outstanding as of the previous session's close, and it does not change while the market is open. The number you are looking at on a 2pm chart is yesterday's book.
Two things follow, and most free charts mention neither.
First, "real-time GEX" is real-time in spot and implied volatility, not in positioning. The strike levels — the walls — are fixed for the session by construction. A tool refreshing every second is repricing the same fixed inventory against a moving spot.
Second, and more important: on an index where same-day expiries dominate the tape, a large share of the day's actual gamma is created and destroyed inside the session and never appears on an open-interest chart until the next morning. Cboe reported that 0DTE contracts made up 60% of total SPX volume in September 2025, in a month averaging 4.26 million SPX contracts a day. An OI-based chart is blind to the majority of that flow while it is happening. If the volume-versus-positioning distinction is new, options volume vs open interest is the prerequisite.
Free tiers then add their own lag on top of the structural one. FlashAlpha, for instance, documents a cache of up to 15 minutes on its free API tier, against 15 seconds or better once you pay. That is a reasonable trade for free data — it is only a problem if you did not know it was there.
Check two: how many expirations are in the number?
This is the single largest source of disagreement between two charts of the same underlying, and it is almost never displayed next to the level.
Barchart's $SPX gamma exposure page states its method openly: gamma exposure calculated on four nearby expirations, based on a 1% move of the underlying, using gamma and open interest from the consolidated OPRA feed. FlashAlpha's free tier returns a single expiration, with full-chain aggregation reserved for a paid plan. A full SPX chain, by contrast, runs to roughly 21,000 listed contracts across every expiry.
A four-expiry GEX number and a full-chain GEX number are different quantities that share a name. Neither is wrong. But you cannot compare a level from one against a level from the other, and a wall built by far-dated positioning simply does not exist in a near-expiry chart. If a monthly or quarterly strike is anchoring the tape, a near-term chart will show you a clean, uneventful profile right up until price refuses to go through a level it never plotted.
Check three: whose sign convention is it?
Calls positive, puts negative, dealer perspective is the common default. Some tools invert it and present the customer's book instead. The symptom is unmistakable once you know to look for it: your "positive gamma, suppressed volatility" regime is another chart's negative-gamma regime, on identical data.
The tell is in the language rather than the numbers. If the chart describes positive gamma as suppressing moves and pinning price toward large strikes, it is on the dealer convention. If it does not say, treat the sign as unknown until you can identify the regime from the tape. The GEX flip price explains what the crossover point means and why it is the level most worth watching.
Check four: what are the units?
Gamma exposure gets published as dollars per 1% move, as shares of delta per point, as raw contract-gamma, and as an unlabelled index. All four are defensible. Only one of them is on the chart in front of you.
Units do not matter for reading shape — where the walls are, where the flip sits, whether the profile is lopsided. They matter enormously the moment you compare today against last week, one ticker against another, or try to reason about whether a given gamma figure is large. If the axis is unlabelled, use the shape and discard the magnitude.
Where the free charts actually are
SpotGamma publishes a free daily SPX gamma exposure chart alongside its paid platform, with the dealer assumption stated on the page. Daily update cadence, index only.
Barchart carries gamma exposure on its $SPX quote page, calculated through the day off the consolidated OPRA feed, with the four-expiration methodology disclosed.
FlashAlpha covers 6,000+ US tickers with computed walls and gamma flip, on a free tier limited to five API requests a day, single-expiration queries, and a 15-minute cache against 15 seconds or better on paid plans. The free tier covers individual equities; ETF symbols such as SPY and QQQ are gated to paid plans.
MenthorQ, GEX-Metrix and QuantWheel all run free tiers built around a single index or a limited slice of the chain, typically with history or ticker breadth behind the paywall.
TradingView community scripts are free and numerous, and the assumptions are whichever ones the script author made. The source is readable — read it before trusting the output.
SquawkFlow's free SPX GEX chart takes the full-chain approach: a snapshot built each morning before the open from CBOE settlement open interest across roughly 21,000 SPX contracts, crossed with Schwab implied volatility, refreshed every 30 minutes through the cash session, no signup. It also publishes how often each wall has actually held, which is the one number that tells you whether a level has been worth respecting. Its walls are fixed for the session too, for exactly the reason in check one — that constraint is structural, not a vendor choice.
Reading one once you have picked it
Three features carry almost all the information.
The zero-gamma flip is where net dealer gamma crosses zero, separating the suppressive regime from the amplifying one. Price crossing it tends to change the character of the tape rather than its direction.
The call wall and put wall are the largest positive and negative gamma concentrations, and they behave as soft magnets and soft barriers rather than hard levels. Call wall and put wall explained covers how they typically resolve.
The shape between them matters more than any single number. A tall, narrow profile centred on spot is a pinned tape. A flat profile with the flip nearby is a market with nothing structural holding it.
What none of it tells you is direction. Gamma exposure describes the hedging environment a move happens in — whether flow gets damped or amplified once it starts. It is context for a trade you already have a reason to take, not a reason to take one.
A workable routine takes five minutes: identify the chart's expiration set and units before anything else, locate the flip relative to spot, note the nearest wall above and below, decide from the flip whether you are in a mean-reverting or trend-extending regime, and then size accordingly. If two free charts disagree, the answer is almost always in check one or check two, and it is usually check two.
Free gamma exposure data is genuinely good now. It just requires knowing which four questions the free version quietly answered for you.
Educational content, not financial advice. See our risk disclosure.