Open Interest Magnets: Where Price Wants to Pin Into Expiration

Why Open Interest Moves Price

Every open option contract someone has to hedge. When a strike builds tens of thousands of contracts of open interest, dealers who are short that strike own a nonzero delta that grows as expiration approaches. Pinning is what happens when dealer gamma gets so concentrated at one strike that the aggregate hedging flow drags spot toward that strike into Friday's close. It isn't mysticism — it's observable, repeatable, and measurable from the options chain itself.

What the Open Interest Card Shows

The Options Open Interest card visualizes the full strike-by-strike OI distribution for the upcoming expiration, separating calls and puts. It surfaces three things directly: the max-pain strike (the price at which the aggregate option value to holders is minimized), the largest call and put walls, and the put/call OI ratio across the chain. Strikes that gained OI in the last 5 sessions are flagged — those are the strikes new positioning is being built around, which matter more than legacy interest.

Reading the Signal

Call walls above spot act as resistance because dealers short those calls have to sell into rallies to stay delta-neutral. Put walls below spot act as support for the same reason in reverse. Into the last week of a monthly expiration, spot often chops inside the band formed by the biggest call wall above and put wall below — the classic "pin" behavior. Breaking through a wall on heavy volume reverses the dynamic: dealers have to chase, and moves extend. The max-pain strike is a weaker signal on its own but a useful tiebreaker when call and put walls are roughly balanced.

Where It Fits

Open interest tells you *where* the gamma lives; GEX Summary tells you *how* that gamma affects realized volatility. Use them together: OI walls to pick your short strikes, GEX sign to decide whether to structure the trade as premium-selling (positive GEX regime) or premium-buying (negative GEX regime). Pair with the Key Metrics card for the vol context.

Open the Open Interest card → /app/stocks/AAPL/sentiment