The hedging loop in three steps
Dealers who take the other side of options trades usually hedge to stay delta neutral. Gamma decides which way that hedging pushes the market.
- Dealers long gamma (positive GEX). SpotGamma describes it this way: "when dealers are long options, they must sell underlying stock or futures as price rallies, or buy as price dips—stabilizing price action and reducing realized volatility" (>SpotGamma). That is the pin.
- Dealers short gamma (negative GEX). Dealers "must buy as the market rallies and sell as it drops," which adds fuel to trends (>SpotGamma). That is the whip.
- Expiry resets the board. 0DTE contracts are gone by the close. SpotGamma warns that they "expire quickly, which can in turn lead to erratic price action as dealer hedges rapidly unwind" (>SpotGamma).
For a fuller primer on walls and zero-gamma, see our GEX explainer.
Why 0DTE makes the effect sharper
Gamma is highest for at-the-money options close to expiry. SpotGamma notes that "as expiration approaches, gamma spikes for at-the-money strikes," so 0DTE hedging flows intensify through the afternoon (>SpotGamma).
There is also a structural point in SpotGamma's January 2026 note. If short-dated sellers are the main source of positive gamma, "market stability remains tenuous, dependent on the daily entrance of short-dated options sellers" (>SpotGamma). A pin built on same-day contracts has to be rebuilt every morning.
The other side: how big is the flow, really?
Cboe has studied this directly and reaches a more cautious conclusion.
- In a 2023 analysis, Cboe estimated 0DTE hedging flows at "between 0.04% to 0.17% of the daily S&P futures liquidity" and found "no discernible market impact from 0DTE option trading" (>Cboe).
- In 2025, Cboe put net market-maker gamma hedging at "at best, just 0.2% of the SPX daily liquidity," with customer activity "extremely balanced" (>Cboe).
- In one case study from August 15, 2023, market makers were long about $2bn of gamma during a late-day selloff. That means their hedging would have dampened the drop (>Cboe).
A fair reading of both sources: 0DTE flow can shape intraday levels, especially near large strikes. Cboe's data says net dealer hedging is small next to total S&P liquidity. Treat gamma as a map of where hedging pressure may sit. It does not predict the market.
| View | Pin (positive gamma) | Whip (negative gamma) |
|---|---|---|
| Dealer hedging | Against the move | With the move |
| Typical session shape | Range, price drawn to big strikes | Trend days, broken levels |
| 0DTE role | Short-dated sellers add positive gamma | Hedges unwind at expiry |
| Main caution | Cboe finds net 0DTE hedging is small | Regime can flip within a session |
What Loomi's own gamma study found
Loomi.Ai ran its own dealer-gamma study, published on the GEX Regime page. It tested QQQ, not SPX, so read these as a related market and not a measurement of the S&P.
The pin shows up in the data. - Both walls held and price pinned between them on 30.6% of positive-gamma days, versus 23.1% of negative-gamma days. - Price bounced off the near-term wall 67–93% of the times it was tested. On positive-gamma days the put wall held 93–95%.
So does the whip. - Strongly positive gamma (over +$2bn) gave a next-day move around 0.6%. Negative gamma gave about 1.0%. - Moves past 1.5% came at roughly twice the rate in negative gamma (the page cites 23% against 47%). Comparing only the extremes, beyond −$4bn against beyond +$4bn, the gap widened to about 4×.
Timing matches the 0DTE story. - 73% of call-wall touches and 52% of put-wall touches came in the first 30 minutes. Loomi notes that "after 11am the wall trade is largely gone for the day."
Which side held up. - Buying the bounce lost roughly 0.15–0.33%, and "every long-option variant we tested came out negative after real costs." - Defined-risk put credit spreads on positive-gamma days returned +12% with a 95% win rate. Loomi states this is the only structure with a measured number.
Caveats Loomi publishes with it. The study covered QQQ only, 189 trading days from September 2025 to June 2026, one macro regime. Fills were modeled on 5-minute bars. The +12% / 95% figures "were measured on the study's own spread construction, not specifically at 0DTE." The wall-touch rates come from high/low data flagged as unreliable, so Loomi calls them "indicative, not settled." The credit-spread leg has not been crash-tested.
How to use it on the Loomi.Ai Desk
The GEX Regime page turns the pin-or-whip question into a live reading.
- Regime label. Net dealer gamma per name, in dollars. At +$2bn or more it reads POSITIVE GAMMA: "Dealers dampen moves." At −$1bn or below it reads NEGATIVE GAMMA: "Dealers amplify moves. Walls stop holding." In between, it reads NEUTRAL, and the strategy treats that as no-trade.
- Wall proximity warning. Inside 0.25% of a wall is the trigger zone, and inside 1.0% is a heads-up. The warning stands down the moment gamma turns negative.
- Stale-data guard. If the feed is more than 120 minutes old, "Nothing is shown rather than a stale number."
- Dealer's Hand. This strategy sells only in positive gamma, waits for price to reach the wall and uses defined risk. 0DTE positions are closed in the last half hour.
One thing to know before you look for it: the 0DTE credit-spread ladder is not live yet. Loomi's page says "the ranked 0DTE ladder and the streak pause are in build and are not live yet." Today the Desk gives you the regime and the wall warning. The ranked spread list is still in development.
The Desk costs $8/mo intro, then $20/mo. Dealer gamma, options flow and dark pool data are included.
Put the research to work on your Desk
Explore the tools behind the research, compare the available access, or open your Desk if you already have an account.
FAQ
Do 0DTE options pin the S&P 500? They can add to a pin when dealers are long gamma near big strikes. Cboe's research finds net 0DTE hedging is small relative to S&P liquidity, so treat pinning as a tendency.
What happens when gamma turns negative? Dealers hedge with the move, which can extend trends. In Loomi's QQQ study, negative gamma came with larger next-day moves (about 1.0% versus 0.6%).
When is 0DTE gamma strongest? Close to expiry, at the money. SpotGamma points to 2:00 to 3:30 PM ET as the peak window.
Is Loomi's 0DTE ladder available? Not yet. The regime reading and wall warning are live. The ranked 0DTE ladder is in build.
Loomi.Ai provides educational market research, not financial advice. Study results are hypothetical, measured on QQQ only, and do not guarantee future results.
Sources
- >Record 0DTE volume reshapes the S&P 500, SpotGamma
- >0DTE Options: The Complete Guide, SpotGamma
- >Volatility Insights: Evaluating the Market Impact of SPX 0DTE Options, Cboe
- >0DTEs Decoded: Positioning, Trends and Market Impact, Cboe
- GEX Regime: Dealer Gamma, Walls and the Credit-Spread Ladder, Loomi.Ai