Delta is the most compact order flow statistic: for one candle, the volume initiated by buyers minus the volume initiated by sellers. One number that says which side pushed harder.
Every trade has an aggressor: the order that crossed the spread to make it happen. Trades executing at the ask are buyer-initiated; trades at the bid are seller-initiated. Classifying each tick this way and netting the volumes gives the bar's delta. VolumeLens performs this classification once per tick on live NSE depth data, feeding delta bars, footprints and CVD from the same source.
Delta is most informative when compared to what price did with it:
The mismatches — effort without result — are where delta earns its place on the chart.
Two bars with identical volume can carry opposite deltas. Volume measures participation; delta measures direction of aggression. Reading them together is strictly more informative than either alone.
There is no universal threshold — delta is relative to the instrument's normal activity. Comparing today's delta to the stock's own recent distribution is the meaningful comparison.
Because passive limit buyers can absorb aggressive selling. Sellers crossed the spread (negative delta), but the resting bids were large enough that price still rose.
No. Delta classifies executed volume by aggressor side within the session. Open interest measures outstanding derivative contracts and changes on position creation/closure.