Open Interest is the number of MIDCAP 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 MIDCAP 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.
MIDCAP NIFTY (Nifty Midcap Select) tracks a basket of liquid midcap stocks — a thinner, more volatile chain than the large-cap indices. OI tells you where positions sit, not which way price will go, so read it with the MIDCAP 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.