Pinning is the tendency of a stock to drift toward - and stick near - a strike with heavy options open interest as expiration approaches. Max pain is the strike at which the largest dollar value of options would expire worthless, i.e., the price that causes the most aggregate "pain" to option buyers.

The mechanic

Pinning is driven by dealer hedging. Near expiration, dealers holding large positions at a heavily-populated strike adjust their stock hedges as price wobbles around that strike - buying just below it and selling just above it to stay neutral. That back-and-forth hedging can act like a magnet, dampening moves and holding price near the strike into the close.

How much to trust it

Here is the honest part: pinning is a real tendency, not a law. It is strongest in calm markets with concentrated open interest and weakest when a genuine catalyst overwhelms the hedging flow. "Max pain" gets over-marketed as a price target - treat it as one contextual input about where hedging pressure sits, not a prophecy. A news shock will blow through max pain without a second thought.

Pinning is gravity, not a wall. A big enough catalyst is escape velocity.

Where it fits

Pinning is another expression of the same theme running through modern index trading: dealer positioning shapes intraday behavior. Read it alongside open interest and the volatility regime, and it becomes a useful piece of context for how a session might close - not a standalone trade.