Gap Up
A gap up occurs when a security's opening price is higher than the previous session's high, leaving a visible price gap on the chart where no trading occurred. On NSE, gap ups in Nifty and Bank Nifty futures frequently reflect overnight developments in global markets or significant domestic news events.
Gaps form because the auction-based opening mechanism on NSE determines the opening price based on pre-market orders, which can price in developments that occurred after the previous session closed. When significant positive news emerges — strong US market close, favourable economic data, a positive RBI policy announcement, or a major earnings beat — Nifty futures may gap up at the open, with the opening trade well above the prior day's high.
Gap analysis in technical analysis identifies different types of gaps by their context. A breakaway gap occurs at the beginning of a new trend move, when price breaks out of a consolidation zone on high volume. A runaway or continuation gap occurs mid-trend, reflecting accelerating momentum. An exhaustion gap appears near the end of a trend when momentum is fading. Each type carries a different analytical implication, though correctly identifying the type prospectively is challenging.
In Indian markets, overnight gap ups or gap downs caused by global market movements — particularly the US markets close and overnight futures activity — were among the most common sources of opening volatility. NSE equity markets had no pre-market or after-market trading for equities, meaning all overnight price adjustment occurred instantaneously at the market open. This made gap management an important aspect of overnight position risk in NSE F&O.
Gap fill — the tendency of price to return to the gap zone and 'fill' it by trading through the area where no transactions occurred — has been observed as a frequent intraday and short-term pattern in Indian markets. Gap fills on Nifty were particularly noted on smaller overnight gaps (1–0.3% of index value), where intraday price discovery often retraced to cover the gap before resuming in the original direction. Large gaps driven by fundamental news were less reliably filled in the short term.
A misconception is that all gaps are eventually filled. While many gaps in range-bound markets do get filled, breakaway gaps in strongly trending markets can remain unfilled for extended periods or permanently. The gap-fill tendency is a statistical observation across a large number of instances, not a rule that applies to every individual gap.