Trading glossary
Chart pattern
By the PatternX team · Published
Definition
A chart pattern is a recurring shape that price traces on a chart, such as a triangle, flag or head and shoulders, which traders use to judge whether a move is more likely to continue or to reverse.
How it works
A chart pattern is built from a few reference points, usually swing highs and lows, and the lines drawn through them. Most classic patterns go through the same three stages:
- Formation. Price builds a recognizable structure: a sideways box, a narrowing triangle, a pole and flag, or two or three peaks at similar levels.
- Breakout. Price closes beyond the boundary that defines the pattern, such as a neckline or a trendline.
- Projection. The pattern's height, projected from the breakout, gives a rough measured-move target, and the far side of the structure shows where the idea is wrong.
Patterns are grouped by what they usually imply. Continuation patterns, such as flags and rectangles, suggest the prior trend resumes; reversal patterns, such as double tops and head and shoulders, suggest it is ending.
Why it matters
A pattern turns a vague impression into a plan with three numbers: an entry, an exit if wrong, and a target. That makes risk definable before you commit money and makes trades comparable. It does not make the outcome certain. Patterns describe tendencies in crowd behavior, and many fail, stall or break the other way.
Example
For example, suppose a stock rallies from $40 to $50, then moves sideways between $48 and $50 for two weeks on shrinking volume. That is a rectangle-shaped pause after an advance. A move above $50 would be the breakout, the $2 box height projected from $50 points to roughly $52, and a fall back below $48 would undermine the setup.
Common mistakes
- Seeing shapes everywhere. If you have to squint, it probably isn't there. Write the rules down before you look.
- Acting before the breakout. Until the boundary breaks, a formation is only a range.
- Ignoring context. The same shape means less in a thin, choppy market than in a liquid, trending one.
How PatternX uses it
PatternX runs 20 rule-based detectors, one for each pattern in its pattern library, on every scan. Each reads a fixed trailing window of candles, for example 80 bars for the cup and handle and 90 for head and shoulders, so formations larger than that window aren't seen. A detector returns at most one match, and only when the breakout is on the latest bar, which may still be forming. Every match then passes the same market filters and is graded by the PatternX Score, where each detector's geometry score is capped at 85. See pattern detection.