Positioning & Flow
Open Interest (OI)
Also called: OI
Open interest is the number of option contracts for a given strike and expiration that are currently open: opened but not yet closed, exercised or expired. It is updated once per day after the close.
Volume counts contracts traded today; open interest counts contracts still outstanding. A trade that opens a new position for both parties adds one to open interest, a trade that closes for both parties subtracts one, and a trade between an opener and a closer leaves it unchanged.
Rising open interest confirms that new money is entering a strike; falling open interest means positions are being unwound. Volume far above existing open interest is the classic signature of unusual options activity, since it implies fresh positioning rather than existing holders rolling.
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Frequently asked questions
Why is open interest not updated in real time?
The Options Clearing Corporation reconciles opening and closing transactions overnight, so the figure shown during the session reflects the prior day's close.
Is high open interest good?
It usually means tight bid-ask spreads and easy exits. Whether it is bullish or bearish depends on who opened the positions and why, which volume, trade side and flow data help infer.