Open interest

Open interest is the total number of outstanding options contracts that have not yet been closed, exercised, or expired. It represents the total live exposure in a specific contract at any point in time.

Open interest increases when new contracts are created (a buyer and seller open new positions) and decreases when existing contracts are closed, exercised, or expire.

Open interest vs volume:

• Volume counts contracts traded during a single day and resets to zero each morning
• Open interest accumulates over time and only changes when positions are opened or closed net

High volume with rising open interest signals new money entering the market. High volume with falling open interest signals existing positions being closed.

Why it matters for options traders:

• Liquidity signal: High open interest at a strike means tighter bid-ask spreads and easier fills
• Pin risk indicator: Large open interest concentrations near the current price heading into OPEX can cause the stock to "pin" to that strike
• Sentiment gauge: Large OI buildup at specific strikes can indicate where institutional traders expect the stock to be at expiration

Example: AAPL has 50,000 contracts of open interest at the $200 call expiring this month. This indicates substantial positioning at that level, a potential magnet for price action heading into OPEX.

Related terms: Pin risk, OPEX, liquidity, volume, bid-ask spread

Try it on Stryke: Sort by open interest in the Options Screener to identify the most active strikes and contracts.