Every F&O stock classified into Long Buildup, Short Covering, Short Buildup, or Long Unwinding — refreshed daily from official end-of-day data.
Open interest tells you the size of the outstanding futures position. Open interest change tells you whether that position is growing or shrinking. Combined with the price move, the joint signal becomes one of four classifications — and those four classifications are the foundation of derivative-flow reading.
Strota's OI buildup screener runs this classification on every F&O stock every trading day, using aggregated open interest across all expiries so expiry-week rollover noise doesn't contaminate the signal.
Long Buildup — price up, OI up. The price rose and open interest rose, meaning new long positions are being added at higher prices. This is the strongest bullish signal a futures market gives. Buyers are willing to pay up to enter; they're not just covering shorts. Stocks in persistent Long Buildup over multiple sessions are accumulation candidates.
Short Covering — price up, OI down. The price rose but open interest fell, meaning existing shorts are closing out. The move is real, but it's powered by exits rather than new entries. Short-covering rallies can be sharp but historically fade unless fresh buying follows. Treat as a relief move, not a trend change.
Short Buildup — price down, OI up. The price fell and open interest rose, meaning new short positions are being added on weakness. This often precedes further downside until shorts are forced to cover. The bearish mirror of Long Buildup.
Long Unwinding — price down, OI down. The price fell and open interest fell, meaning existing longs are exiting. The move down lacks the conviction of fresh selling — it's holders giving up, not new sellers piling in. Bearish but weaker than Short Buildup.
On expiry-week days, the front-month contract's open interest collapses simply because positions are rolling forward to the next month. A naive front-month-only OI signal would flag every single F&O stock as 'Long Unwinding' during expiry week — purely as an artefact of rollover.
By summing open interest across all listed expiries per stock and computing the change against the prior day's same aggregate, the rollover washes out and you read the actual positioning shift. This is one of the reasons Strota's classification stays interpretable during the chaotic week of expiry, where most other dashboards' OI signals become unreliable.
Two extra screeners build on the same data:
Unusual OI Buildup — stocks with +/- 20% or larger OI moves today. These are the day's positioning outliers, far above the average daily OI change of a few percent. Listed separately because they're the most actionable extremes.
Futures Basis Screener — premium or discount of front-month futures to spot. Premium = bullish carry (futures trading above spot); discount = bearish carry. A stock with a 0.5%+ discount alongside Short Buildup is a particularly strong bearish setup.
Long Buildup = new longs entering. Short Covering = existing shorts exiting. The first has fresh demand behind it; the second doesn't. Long Buildup has more follow-through historically.
The classification logic is identical for both. Strota's stock-level screener uses stock-future data; FII/DII positioning on index futures is covered separately in the Institutional Positioning section.
Once per trading day, around 6:30-7:00 PM IST when end-of-day derivatives data is published.
Strota's tagging system has been backtested over 376 trading days against 1d/3d/5d forward Nifty/BankNifty returns. Long Buildup and Short Covering showed measurable lift over baseline; Long Unwinding and Short Buildup did the same on the bearish side. Backtest stats are visible on each /tag/