Open Interest (Options)
The total number of outstanding (unclosed) option contracts at a given strike and expiry. Rising OI confirms new money entering; it gauges liquidity and where positioning is concentrated.
Open interest (OI) is the count of all option contracts that have been opened but not yet closed, expired, or exercised at a specific strike and expiration. Unlike volume (which resets daily), OI is a cumulative running total.
Rising OI alongside price movement confirms that new money is entering the market and supporting the move. Falling OI on a price move suggests existing positions are closing — a less convincing signal. High OI at a particular strike can act as a gravitational level into expiry.
OI is also used to assess liquidity: strikes with high OI typically have tighter bid-ask spreads and are easier to fill in size. Very low OI strikes may be difficult to exit without significant slippage.