Gamma Squeeze Explained: When Options Flow Actually Moves a Stock

You’ve seen the post. A green screenshot, a ticker, and a caption: “$5 MILLION in calls just hit — Wall Street HAS to buy now.” The replies fill with rocket emojis. The implication is simple and thrilling: someone made a giant options bet, so the stock must go up.

It feels obvious. It’s usually wrong.

By the end of this lesson you’ll be able to look at one of those “huge call buying” headlines and make a single, confident call: is this worth my attention, or is it probably noise? We’ll build the mechanics only once you can see why they matter.

Why big options volume is not enough

The most common trap is assuming gross volume tells you what happens next. It rarely does. A screenshot of “50,000 calls traded” shows you a number — and hides the four things that actually matter:

1. 1

   Buying or selling?

   For every contract bought, one was sold. The screenshot doesn’t tell you which side the customer was on.

   The tellDirection is unknown from volume alone.

2. 2

   Opening or closing?

   A trader closing an old position creates volume without adding any new exposure to the market.

   The tellClosing flow leaves no fire to feed.

3. 3

   One bet or a spread?

   Many “big” trades are spreads, where one leg offsets the other and little directional risk survives.

   The tellThe legs can cancel each other out.

4. 4

   Who holds the risk?

   The whole mechanism depends on what risk stays with the dealers who facilitate the trade — invisible from the outside.

   The tellNo net dealer risk, no squeeze.

Cboe — the exchange that lists S&P 500 options — has made this point bluntly using its own transaction data: “What matters is the balance of the volume between buys vs. sells, not the total size of the volume” (Cboe, September 2023). If customers buy 50,000 contracts and other customers sell 50,000 of the same contract, the net new risk is roughly zero — however dramatic the headline looks.

The questions that actually matter

If gross volume isn’t the signal, what is? When flow does move a stock, it comes down to three checks. Here’s the whole framework up front — keep it in your pocket as you read, and we’ll earn each one with the mechanics below.

1. 1

   Net, not gross

   Is the flow genuinely one-sided and opening — or is it balanced, spread, or closing?

   The tellBalanced or closing flow usually means no fire.

2. 2

   Room to matter

   Is the stock small or illiquid enough for hedging to move it — or a mega-cap/index deep enough to absorb the flow?

   The tellLiquidity decides whether the hedge is even felt.

3. 3

   Confirmation

   Is price actually moving with the flow, backed by volume and rising implied volatility?

   The tellA flat chart under a loud screenshot is noise.

Just enough mechanics: delta, gamma, and hedging

Now the machinery — kept deliberately simple, using definitions from the Options Industry Council (OIC) and The Options Clearing Corporation (OCC). A call option gives its buyer the right (not the obligation) to buy a stock at a set “strike” price before expiration, for a premium — like a refundable reservation to buy at today’s price even if it climbs later.

Delta is speed

The OCC defines delta as the “expected change in an option’s price… for each $1.00 move in underlying stock price.” It also tells a dealer roughly how many shares they’d need to stay hedged.

Gamma is acceleration

Delta isn’t fixed — it changes as the stock moves, and gamma measures how fast. The OCC literally calls gamma the “acceleration of delta.” Gamma is highest for at-the-money options and grows as expiration approaches, so a dealer’s hedge needs can change quickly on small moves.

Why dealers hedge — and the hinge of the whole story

A market maker isn’t trying to bet on direction — they want to earn the spread and stay neutral. When they sell you a call, they inherit risk, so they offset it, often by buying or selling the underlying. Because delta keeps changing, this delta hedging is continuous. Which way it pushes depends on one thing:

1. 1

   Short gamma → amplifies

   Dealers who sold the options must hedge with the move — buy as the stock rises, sell as it falls.

   The tellHedging adds fuel; a move can feed on itself.

2. 2

   Long gamma → dampens

   Dealers who bought the options hedge against the move — sell into rallies, buy into dips.

   The tellHedging absorbs the move and smothers volatility.

Don’t just take that on faith — play with it. Move spot toward the strike and shorten the expiry to see how many shares a dealer must chase, then flip the dealer from short to long and watch the same hedging reverse from fuel to brake.

When the alarm is a real fire

Put the pieces together and here’s the actual gamma-squeeze loop, in the specific conditions where it can ignite:

1. Traders buy a lot of short-dated calls, concentrated near the current price.
2. Dealers sell or facilitate those calls and are left short gamma.
3. To stay hedged, dealers buy the underlying stock.
4. That buying (plus the original demand) nudges the price up.
5. As price rises toward the strikes, delta rises — because gamma is high.
6. Dealers must buy even more to stay hedged.
7. Under the right conditions — dealers net short gamma, flow not offset, a stock thin enough to be moved — step 6 reinforces step 4, and the loop can feed on itself.

Notice the language: can, under the right conditions. This is a setup worth monitoring, not a guarantee — and it has a built-in expiration date. As the options expire or get rolled, and as implied volatility falls, the hedging demand that powered the move can vanish, sometimes quickly. The same mechanism that lifted the stock can reverse, which is why chasing a squeeze into expiration is the classic way to get hurt.

When it’s burnt toast

This is the section most “gamma squeeze” content skips — and it’s where the credibility lives. Far more often than not, the alarm is burnt toast. For every exciting-sounding read, there’s a calmer explanation that usually fits better:

0DTE options: fast doesn’t always mean big

No topic generates more squeeze anxiety than 0DTE options — contracts that expire the same day. The fear is intuitive: if gamma is highest near expiration, options expiring in hours must be the most explosive of all. It’s true 0DTE compresses everything — but “fast” isn’t the same as “big,” and here the data is unusually clear, because Cboe (where S&P 500 options trade) can see whether each transaction is customer or dealer, buy or sell.

The volume really did explode

But the net dealer risk stayed tiny

Despite that volume, Cboe found 0DTE customer flow is remarkably balanced — over 95% of SPX 0DTE trades are limited-risk structures (long options or spreads), with only about 4% in naked short options (Cboe, 2025). So the risk left with dealers is a rounding error next to the market it trades in:

It even holds on the days commentators blame on 0DTE. On August 15, 2023, the strike everyone pointed at traded more than 100,000 contracts — but customer buys and sells nearly offset, and dealers were actually long gamma by mid-afternoon (which dampens a move, not amplifies it):

Cboe’s conclusion: despite the huge notional volume, there’s “no discernible market impact” on the index’s intraday volatility. In plain terms — high 0DTE volume does not automatically mean high market impact. Net exposure and liquidity decide.

Honest case studies

Labels matter. Here are four cases at a glance, each tagged by how strong the evidence actually is — then the detail behind each badge.

GameStop, January 2021 — commonly claimed, evidence is mixed

This is the case everyone cites — and the one the primary evidence complicates. The SEC’s October 2021 staff report stated it “did not find evidence of a gamma squeeze in GME during January 2021.” The rise in options volume was “mostly driven by an increase in the buying of put, rather than call, options,” and “market-makers were buying, rather than writing, call options” — patterns the SEC said are “not consistent with a gamma squeeze.” Short interest was extraordinary (above 100% of float — about 123% in January 2021), and staff attributed the run-up to “positive sentiment.” Some academics later argued the report understated options hedging, so the honest verdict is contested — not the tidy gamma-squeeze story the internet told.

AMC, June 2021 — plausible but hard to prove (media-described)

The strongest single-stock candidate. Reuters reported AMC’s record surge (the stock closed up 95.2% to $62.55 on June 2, 2021) was “partly fueled” by options, with analysts saying market-makers “likely” bought shares to hedge sold calls — a gamma-squeeze dynamic. The options activity was real and huge: roughly 233,000 contracts in a single bullish strike, and 4.6 million AMC option contracts overall that day. But notice the hedged language — “likely,” “analysts said.” And the confounds are everywhere: a frenzy of retail attention, an investor-promotion campaign, and a large holder publicly selling its stake. Even with every visible ingredient present, you can’t isolate dealer hedging as the cause from public data. That honesty is the point.

Earnings moves — an educational principle, not a squeeze

Around earnings, options price in an expected move (you can estimate it from at-the-money option prices). That implied move forecasts magnitude, not direction. When the stock then jumps, it’s tempting to say “options caused it” — but the news caused it. Options often price a larger move than the stock actually makes, which is why implied volatility usually collapses afterward — the famous “IV crush.” Options predicted volatility; they didn’t create the result.

Run the 3-question filter yourself

You met these three questions up top. Here they are as a checklist you can actually run the next time a “huge call buying” screenshot lands in your feed. Tap each one you can confidently answer.

How MarketDecode helps you run the check

You don’t need a Bloomberg Terminal to run that filter — you need the right pieces in one place. Here’s the 60-second pass inside MarketDecode:

1. 1

   Options Flow

   Total premium, the bullish/bearish split, the call/put ratio, unusual-activity flags, sweep count, and the top institutional trades.

   The tellYour “net, not gross” gut check.

2. 2

   Price Pulse

   Price, the day’s range, volume vs. average, and how the stock is moving relative to the S&P.

   The tellIs the underlying actually confirming?

3. 3

   Story Card

   A plain-English summary of what’s really driving the name — earnings, a product, an analyst move.

   The tellIs there a real catalyst behind the flow?

4. 4

   AI Decision

   An action bias, its confidence, the top reasons, and a contradiction count when signals disagree.

   The tellDoes the options signal agree with the rest?

5. 5

   Risk Watchlist

   Severity-rated risks like an upcoming expiration or an IV-crush setup, framed as things to monitor.

   The tellWhat could reverse this?

Final takeaway

A gamma squeeze is a real market mechanism — but a mechanism, not a meme label you paste onto any green candle. Most of the time, a “huge call buying” headline is burnt toast: dramatic volume that nets to little real exposure. Occasionally, in a thin enough stock with lopsided enough flow, it’s a real fire.

Big options flow deserves your attention, not your obedience. The edge isn’t reacting faster than everyone else to the screenshot — it’s asking better questions before you chase: Net or gross? Room to matter? Is price confirming?

Common questions

What is a gamma squeeze in simple terms?

A feedback loop where dealers who sold call options have to buy the underlying stock to stay hedged, and that buying can push the price higher — forcing them to buy even more. It can happen, but only under specific conditions: dealers left net short gamma, flow that isn’t offset, and a stock liquid enough to trade but thin enough to be moved.

Does big call-option volume mean a stock will go up?

No. Volume is gross; what matters is the net exposure left with dealers after buys and sells offset. As Cboe has shown with its own data, even huge volume can net to almost nothing. Big, unusual options activity can be completely real and still not move the stock.

Was GameStop in 2021 a gamma squeeze?

It’s contested. The SEC’s 2021 staff report said it “did not find evidence of a gamma squeeze” in GME, noting the options surge was mostly put buying and that market-makers were buying, not writing, calls. It attributed the run-up to positive sentiment. Some academics later argued options hedging mattered more than the report concluded — so “contested” is the honest label, not “confirmed.”

Are 0DTE options dangerous for the market?

For the S&P 500 index, the evidence says the fear is overstated. Cboe found that despite enormous 0DTE volume (nearly 2 million contracts a day by 2025), net dealer gamma is a tiny fraction of daily futures liquidity, with no discernible impact on intraday volatility. Single-stock 0DTE is thinner and less studied, so don’t assume the same conclusion there.

What is “IV crush” around earnings?

Before earnings, uncertainty pushes option prices (and implied volatility) up. Once the result is known, that uncertainty disappears and implied volatility usually drops sharply — “IV crush” — which can shrink an option’s value even if the stock moved the way you expected.

Sources

Every figure and quote above is drawn from a primary or authoritative source, stated with original dates because options-market data changes over time. The delta and gamma charts are labeled illustrative teaching examples, not live data.

1. U.S. Securities and Exchange Commission, Staff Report on Equity and Options Market Structure Conditions in Early 2021 (Oct. 18, 2021), sec.gov — GameStop short interest (>100% of float; ~123% in Jan 2021), the put-heavy options surge, dealers buying rather than writing calls, the finding that staff “did not find evidence of a gamma squeeze,” and the “positive sentiment” conclusion.
2. Cboe (Mandy Xu), Much Ado About 0DTEs: Evaluating the Market Impact of SPX 0DTE Options (Sept. 8, 2023), cboe.com — 0DTE growth (≈5% of SPX volume in 2016 to ~half by 2023), “high volume ≠ high risk,” net dealer gamma at ≈0.04%–0.17% of daily S&P futures liquidity, the Aug. 15, 2023 long-gamma case, and no discernible intraday-volatility impact.
3. Cboe (Mandy Xu), 0DTEs Decoded: Positioning, Trends, and Market Impact (May 2, 2025), cboe.com — ~2 million 0DTE contracts a day, over 95% of trades in limited-risk structures (~4% naked short), and net market-maker gamma of roughly 0.2% of SPX daily liquidity.
4. Reuters, Shares of retail favorite AMC nearly double… (June 2, 2021) and Explainer: What is a gamma squeeze and how did it drive up AMC’s stock price? (June 3, 2021), reuters.com — AMC’s +95.2% close to $62.55, ~233,000 contracts in a single bullish strike, 4.6 million AMC option contracts that day, and the analyst-described, explicitly hedged gamma-squeeze dynamic.
5. OCC / Options Industry Council, options education (Understanding Options Greeks; OCC Demystifying the Greeks, 2024), optionseducation.org — definitions of delta (“expected change in an option’s price… for each $1.00 move”) and gamma (the “acceleration of delta”).
6. Academic counterpoint: Ad Hoc Academic Committee on Equity and Options Market Structure Conditions in Early 2021 (SSRN working paper 4030179; summarized at the CLS Blue Sky Blog, Columbia Law School, Feb. 22, 2022) — the argument that options hedging may have mattered more than the SEC concluded, which is why GameStop is labeled “contested.”