Open Interest
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Open interest (OI) is the count of option contracts at a given strike and expiration that have been opened and not yet closed or exercised.
Unlike daily volume — which measures activity for a single session — open interest is a running total that accumulates positioning across sessions. A high-OI strike represents persistent positioning, not just a busy day.
OI is reported daily by the OCC and updates overnight. See also the articles on significance of open interest and find the likely direction.