What Is an Option Chain?
An option chain is a table listing all available strike prices for an expiry, showing CALL data on one side and PUT data on the other, with columns like Open Interest (OI), Change in OI, Implied Volatility (IV), Volume, and Last Traded Price (LTP).
Open Interest (OI)
OI is the total number of outstanding (not yet closed) contracts at a given strike. Unlike volume (which resets each day), OI accumulates and reflects real committed positions.
- Rising OI + rising price = new buying, bullish conviction building.
- Rising OI + falling price = new selling, bearish conviction building.
- Falling OI (regardless of price direction) = positions being closed/unwound, conviction fading.
- Strikes with the highest OI are often viewed as key support (high PUT OI strike) or resistance (high CALL OI strike) levels for that expiry, because large option writers have a strong incentive to defend those levels.