OPEX

OPEX stands for options expiration, specifically the monthly standard expiration date, which falls on the third Friday of each month for standard listed equity options. It's the most significant expiration in any given month because the largest volume of open contracts expires simultaneously.

OPEX is not just a date, it's a market event. The convergence of massive open interest expiring on a single day creates predictable and unusual price dynamics in the days leading up to it.

Why OPEX matters:

Pin risk: Large open interest concentrations at specific strike prices can cause stocks to gravitate toward those strikes as expiration approaches. Market makers delta-hedging their books buy and sell shares to stay neutral, creating price pressure around heavily populated strikes.

Volume and volatility: OPEX week often sees elevated volume, unusual intraday price swings, and increased activity in both the underlying and options market as traders close, roll, and adjust expiring positions.

Gamma exposure: As monthly expiration approaches, gamma peaks for all near-the-money options, making price movements faster and more volatile than at other times of the month.

Quarterly OPEX (triple/quad witching): The third Friday of March, June, September, and December is quadruple witching, when stock options, index options, stock futures, and index futures all expire simultaneously. These dates see the highest OPEX-related volume of the year.

Example: AAPL has 80,000 contracts of open interest at the $190 call heading into OPEX. As the third Friday approaches, market makers may need to buy shares if AAPL rises toward $190, and sell if it falls back, potentially creating a gravitational pull toward the $190 strike.

Related terms: Pin risk, open interest, 0DTE, expiration date, gamma

Try it on Stryke: Track all upcoming OPEX dates in the Options Expiration Calendar.