What it is
Market Profile, developed by Peter Steidlmayer with the Chicago Board of Trade in the 1980s, reorganises a session from a price-against-time chart into a distribution of activity by price. Each price level accumulates a letter, a time-price opportunity, for every interval in which it traded, producing a histogram whose shape describes where the market spent its time. Volume profile is the closely related version that stacks traded volume instead of time.
How it works
The vocabulary is specific. The Point of Control is the price with the most activity. The Value Area is the range containing roughly seventy percent of the session's activity, a convention corresponding to one standard deviation of a normal distribution. High-volume nodes are prices the market accepted; low-volume nodes are prices it rejected and travelled through quickly. The Initial Balance is the range of the first hour, and single prints mark levels that traded only once.
How traders use it
The framework is about acceptance rather than prediction. A balanced, bell-shaped profile suggests a market in equilibrium where the edges of the value area are reasonable places to fade. An elongated or double-distribution profile suggests directional conviction or a regime change part-way through the session. Untested points of control from earlier sessions frequently act as magnets, and low-volume areas tend to be crossed quickly because there is little resting interest inside them.
Where it breaks down
It is a descriptive tool: it explains what has happened with unusual clarity and makes no forecast. Its output also depends entirely on choices the user makes, including the session boundaries, the row height and the volume source. In fragmented equity markets and across crypto venues the volume series differs materially between data providers, and the seventy percent value area is a convention borrowed from a normality assumption that intraday distributions do not satisfy.
Educational reference. This entry describes how a concept is defined and used. It is not investment advice, not a recommendation, and not a signal. Any rule you build from it should be tested with realistic costs before it is traded, and no historical result guarantees a future one.