OPEX (Options Expiration)

What is OPEX (Options Expiration)?

OPEX (Options Expiration) OPEX is the colloquial term for "options expiration" — the day when monthly options contracts expire and settle. In US equity markets, the standard monthly OPEX day is the third Friday of each month. Quarterly OPEX days (March, June, September, December) coincide with index futures expiration, creating "triple witching" days with elevated volume and volatility. OPEX days are significant because: - **High volume in the final hour**: institutional rebalancing of derivatives-equity hedges drives 2-3× normal volume in the last 90 minutes - **Pin-strike pressure**: strikes with concentrated open interest tend to act as gravitational levels - **Realized vol can spike**: dealer hedging flows produce sharper intraday moves - **Settlement mechanics**: cash-settled index options settle at specific calculation methodologies (e.g., SPX settles at the AM opening price on the day after OPEX) Types of OPEX: **Monthly OPEX**: Third Friday of each month. The traditional expiration. Most retail options activity historically centered on monthlies. **Weekly OPEX**: Most major indices (SPX, SPY, QQQ, IWM) and many liquid stocks now have weekly expirations every Friday. Some have additional Wednesday or Monday expirations. **Daily OPEX** (0DTE): SPX, SPY, QQQ now have daily expirations across all weekdays. 0DTE represents 45%+ of SPX options volume in 2025. **Quarterly OPEX** (Triple Witching): March, June, September, December — when stock options, index options, and index futures all expire on the same Friday. Highest volume and volatility of the quarter. OPEX patterns to know: **Pre-OPEX week dynamics**: VIX often drifts higher into Thursday as dealers position for the expiration roll. Open interest dynamics shift dramatically as positions roll forward. **OPEX Friday**: Volume builds throughout the day, peaking in the final hour. Max pain often acts as a gravitational level. Pin-strike strategies have historical edge. **Post-OPEX Monday**: Often shows the reversal pattern from Friday — directional moves attributed to position rebalancing after expiration. OPEX-related strategies: - **OPEX-week iron flies**: short butterflies centered on max pain, profiting from the pin effect - **OPEX-week credit spreads**: selling premium with the expiration as a known event - **Post-OPEX positioning**: opening fresh swing positions on Monday after the OPEX flow has cleared For most retail traders, OPEX awareness matters primarily for: - **Trade timing**: avoid opening new positions in the final hour of OPEX Friday - **Volatility expectations**: realized vol is elevated on OPEX days - **Pin trades**: butterflies, iron flies near concentrated open interest can produce outsized wins on OPEX days - **Roll planning**: rolling positions before OPEX rather than letting them expire avoids assignment risk OPEX is a permanent feature of equity options markets. With the addition of weekly and daily expirations since 2022, every Friday is technically an OPEX, but the third Friday of each month retains the largest open interest and most pronounced dynamics.