Open Interest is the number of BANK NIFTY option contracts that are still open — written but not yet closed out or settled. This page plots call and put OI at every strike on the NSE BANK NIFTY chain, alongside the change in OI. Rising OI at a strike means fresh positions are being built there; falling OI means positions are being unwound. The strikes carrying the heaviest call OI are commonly watched as resistance and the heaviest put OI as support.
BANK NIFTY tracks the most heavily traded banking stocks and moves faster than the broad market, so its option data swings harder through the session. OI tells you where positions sit, not which way price will go, so read it with the BANK NIFTY Put Call Ratio for net sentiment, the max pain strike for the expiry-day magnet, and the option chain for the strike-by-strike detail. All three are linked above.