SPY's call wall, put wall and gamma regime from the latest session on Robinflow's public data, updated every session. See SPY gamma exposure by strike. The live heatmap in the app is current.
Why it matters
Puts are how most large holders protect a position, and the market makers who sell those puts hedge them with stock. Where a lot of puts are open at one strike, that hedging is large. As price falls toward the strike, hedgers who are short those puts have to sell more stock to stay flat, and as price recovers they buy it back. Above the wall, that buying can help a dip find its footing. Below it, the selling side of the same flow is what makes breaks through a put wall move quickly.
The put wall gives you that level as a single number. On a Robinflow symbol page it sits beside the call wall, the spot price at the close and the gamma regime, so you can see whether price is resting on its downside level, holding above it, or already trading below it.
Like the call wall, it moves. Protective puts get rolled down after a rally or closed after a scare, and the wall goes with them.
How the put wall is computed
The put wall comes out of the same gamma exposure calculation as the call wall. Each contract's gamma is multiplied by its open interest and the 100-share multiplier, signed under the standard assumption that dealers are short what customers own (so put open interest adds negative gamma at its strike), and summed by strike across every expiration. The strike with the largest negative total is the put wall. The call wall entry walks through each step.
Robinflow draws that profile as a strike by expiration heatmap on the GEX page, and the guide to how to read gamma exposure shows how the put wall, the call wall and the gamma flip work together on a full chain.
What it does not tell you
- It is not a floor. A put wall marks where hedging pressure is concentrated, not a price that cannot be breached. Heavy selling or bad news goes straight through it.
- It does not say why the puts are there. A wall built from portfolio protection and one built from aggressive bearish bets look the same in the gamma figure but mean different things.
- Definitions differ by source. Many sites define the put wall as the strike with the largest put open interest. Robinflow defines it by gamma concentration. The two can land on different strikes for the same symbol on the same day.
- Public data is delayed. Symbol pages show the session three trading days ago. The live GEX heatmap in the app is current.
What it looks like in the data
MSFT closed the September 11, 2026 session a few cents below its put wall, with the call wall only five dollars higher: a stock pinned between two heavy strikes.
Positive regime: hedging leaned against moves in both directions. The put wall at $495 is the strike where downside hedging was heaviest, and price closed 0.03% below it. Drawn to scale. Not a price target.
| Level | Price | Distance from close | What it marks |
|---|---|---|---|
| Call wall | $500 | +1.0% | Heaviest positive gamma; likely to slow a rally |
| Put wall | $495 | +0.03% | Heaviest negative gamma; where downside hedging concentrates |
| Spot at close | $494.85 | 0.0% | Where the session ended |
Read together: a close a hair below the put wall inside a positive regime, with the call wall one percent overhead. That is a stock the hedging flow was holding in a tight band. Whether it reclaimed the wall or lost it the next day is not something the walls decide.
