The two strikes that frequently bound the index for the expiry week.
Two strikes worth watching on every chain: highest call OI and highest put OI. They mark the levels institutions are most heavily positioned to defend.
Together they form the 'expected range' for the index until expiry.
Highest call OI = the strike with the most call premium collected. Writers defend it by intervening at the cash level.
Highest put OI = same logic on the downside.
Strota highlights both on /nifty-option-chain.
Sell options near the dominant OI strikes — they're the most-defended levels for the week.
Iron condor with shorts at the dominant OI strikes captures the institutional positioning as edge.
Watch for OI shifts — if writers cover dominant call OI, expect resistance breach.
On weekly expiry, the dominant call OI strike caps the high on ~70% of weeks. Dominant put OI strike floors the low ~65% of weeks. The combined range covers 50-55% of weekly index settlements.
It's a high-edge starting point. But check IV regime (selling premium edge) and avoid event weeks.