ADX and the DI pair, kept apart on purpose

What it means

Each bar's directional movement is the part of its range that extended beyond the previous bar, up or down. Those are smoothed and expressed as +DI and −DI, and ADX measures how far apart the two have stayed.

ADX carries no direction. It rises in a strong decline exactly as it does in a strong advance, which is the single most common misreading of it.

How we detect it

The engine reports strength and direction as two separate facts: ADX at or above 25 is called trending, and the direction comes only from which DI line is higher.

There is a floor beneath which the reading is refused. The ratio behind ADX is unstable when both DI lines are near zero — one side being exactly zero makes it read 100 however small the other is — so a market whose highs and lows barely moved is reported as unremarkable rather than as maximally trending.

Unlike the oscillators it is not gated on being near a zone, because it describes how directional the recent past was, which is structural context rather than a momentum extreme.

When the read carries information

• There are enough bars for the double smoothing to settle; ADX needs roughly twice its period before it means anything.
• The market has actually moved, so the directional components are real rather than rounding.

When it misleads

• It lags heavily. By the time ADX confirms a trend, most of the move it is describing has happened.
• A range with wide swings can produce a respectable ADX while going nowhere overall.
• Read without the DI pair it says nothing usable, which is why the two are never separated here.

How it reaches you

It appears as strength and direction in one line, and never as an instruction.

A high reading is a description of the recent past and not a forecast of its continuation.