What is a gap in stock trading?

A gap occurs when a stock opens at a significantly different price than its previous close, creating a visible gap on the chart. This indicates strong overnight sentiment driven by news, earnings, or pre-market activity.

Do all gaps fill eventually?

While many gaps do fill (price returns to the previous close level), not all gaps fill. Strong momentum gaps with high volume and clear catalysts may never fill.

What is the best time to trade gaps?

The first 30 minutes after market open are typically the most volatile for gap trading. Many traders wait for initial price action to settle before entering positions.

How much gap percentage is significant?

A gap of 2% or more is generally considered significant for most stocks. However, volatile stocks may require larger gap thresholds to filter noise.

Gap Signals: Trading Pre-Market Price Gaps

Key Takeaways

Gaps indicate strong overnight sentiment - bullish (gap up) or bearish (gap down)
Volume confirms the strength of the gap - high volume gaps are more significant
Many gaps 'fill' (return to previous close), but strong momentum gaps may not
The first 30 minutes after open are most volatile for gap trading

What are Gap Signals?

A gap occurs when a stock opens at a significantly different price than its previous close, creating a visible gap on the chart. Gaps indicate strong overnight sentiment - either bullish (gap up) or bearish (gap down) - often driven by news, earnings, or pre-market trading activity.

Gap signals are among the most powerful indicators of immediate market sentiment because they represent a shift in perceived value that occurred outside regular trading hours.

Types of Gap Signals in EMMA

Strict Gap Up

The most conservative gap definition. A strict gap up occurs when today's entire price baris above yesterday's high:

Strict Gap Up Condition

Low(today) ≥ High(yesterday) × (1 + threshold%)

This creates a true "gap" on the chart with no overlap. These are rarer but often indicate stronger momentum due to overnight news or institutional buying.

Gap Up

A less strict definition where the open price gaps above yesterday's close:

Gap Up Condition

Open(today) ≥ Close(yesterday) × (1 + threshold%)

More common than strict gaps, these still show bullish overnight sentiment but may fill during the trading day.

Gap Down

The bearish counterpart - price opens significantly below yesterday's close, indicating selling pressure or negative news.

Volume Confirmation

Always check volume when evaluating gap signals. A gap up with 3x average volume is far more significant than one on light volume. High volume confirms institutional participation.

How to Trade Gap Signals

Gap and Go Strategy

When a stock gaps up with high volume, momentum often continues in the gap direction. Traders look for:

Gap > 4% with relative volume > 2x average
Price holding above the gap level (no fill)
Continuation patterns after the open

Gap Fill Strategy

Many gaps "fill" - price returns to the previous close level. Traders may:

Short gap ups that show weakness (fading)
Buy gap downs that show support (reversal)
Use the gap level as a take-profit target

Gap Fill Risk

Not all gaps fill, and betting on a gap fill against strong momentum can be dangerous. Always wait for confirmation that momentum is fading before fading a gap. Look for rejection candles, declining volume, or failure to make new highs.

Key Parameters

Parameter	Default	Description
Threshold	2.0%	Minimum gap size to trigger signal

Real-World Scenarios

Earnings Gap

A company reports better-than-expected earnings after hours. The next morning, the stock gaps up 8% on 5x normal volume. This is a high-conviction gap that often leads to further gains as analysts upgrade their targets.

News Gap

A biotech company receives FDA approval overnight. The stock gaps up 15% at the open. These catalyst-driven gaps often have strong follow-through but can be volatile.

Tips for Using Gap Signals

Check the catalyst: Gaps with news (earnings, upgrades) tend to have more follow-through
Volume matters: High volume gaps are more significant
Time of day: First 30 minutes after open are most volatile
Pre-market levels: Watch pre-market high/low as key intraday levels

Pre-Market Analysis

Check pre-market trading before the open. A gap that's already been tested and held in pre-market may have stronger support than one that opens at pre-market highs and immediately sells off.