Price Gaps: “Gaps Always Fill” – a Myth With a Grain of Truth

A price gap is an area on the chart with no trading, because the market opened above the previous high or below the previous low. The popular saying “gaps get filled” is only partly true and, without a time frame, means very little.

What it is

Classic analysis divides gaps into common, breakaway, continuation and exhaustion gaps. On futures that trade almost around the clock, a “gap” usually means the difference between the close of the regular session and the next open.

In index futures trading, what matters is whether the open is inside or outside the previous day's value area, because that changes the character of the session.

How people use it

trading the gap fill
a gap as a sign of strength and continuation
classifying gaps into types after the fact

What the research and evidence say

Whether a gap fills depends on its size, the context and the time horizon. For small gaps in indices, a fill in the same session is common; for large ones it's much rarer. Classification into types is almost always done after the fact: you recognise an “exhaustion” gap by the fact that the market turned.

Weaknesses

“gaps always fill” without a time horizon is unfalsifiable
gap types are identified after the fact
in round-the-clock markets the definition of a gap depends on the chosen session
large gaps often don't get revisited for a long time

What order flow shows

What matters most on a gap open is what participants do in the first few minutes: whether the market accepts the new prices outside yesterday's value area, or aggressively rejects them and goes back inside. The profile and order flow show this in real time, instead of assuming the gap “has to” fill.

Indicators vs order flow

Every indicator and every pattern in this section is built from the same data: a candle's open, high, low, close and sometimes volume. They're derivatives of price, showing the effect rather than the cause. Order flow looks at what price is made of: who was buying and selling aggressively (delta), where limit orders were waiting (the order book) and at which prices the market accepted trade (the volume profile).

On CME futures this data is real and comes from one central market. Spot forex doesn't have it: platforms show tick volume, the number of price changes at a single provider.

To be fair: order flow isn't the Holy Grail. It takes learning, it can be noisy, big players hide some of their orders, and an edge only comes from a process and risk control. But it gives you information that simply isn't on a candlestick chart.

How to use it sensibly

decide which session you count as the day
distinguish between an open inside and outside the value area
keep statistics for your own instrument instead of repeating general slogans

Glossary: Price gap
Glossary: Value area (VA, VAH, VAL)
Glossary: Regular and overnight session
Glossary: Acceptance and rejection
Atlas of biases: Hindsight bias
Atlas of biases: The gambler's fallacy
Order flow: The Initial Balance and day types: what the first hour says about the whole session
Order flow: Volume profile: how to read the POC, value area, HVNs and LVNs
Also under the microscope: Fibonacci retracements
Also under the microscope: Trend lines
Also under the microscope: Support and resistance

This is the day, week and month Volume Profile in the Hetman Terminal (Volume Bastions). Screenshot from the Hetman Index (IHA) – a training instrument, simulated data. See all the Hetman Terminal tools →

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Frequently asked questions

What is a price gap?

An area on the chart with no trading, when the market opened above the previous high or below the previous low.

Does a gap always fill?

No. Small gaps often fill quickly; large ones may not be revisited for a long time. Without a time frame, the saying means nothing.

Educational content, not investment advice. No signals, entries, stops or position sizes.