ADX measures how strongly a market is trending, without indicating which way. It's derived from the +DI and −DI directional indicators (which track upward vs. downward price movement), smoothed into a single strength reading. Readings above roughly 25 are conventionally read as a genuine trend; below that, the market is considered directionless, chop rather than trend.
Because ADX only measures strength, it's almost always paired with the +DI/−DI lines (or another directional signal) to determine direction. ADX confirms there's a real trend here, while +DI above −DI (or a moving-average relationship) says which way it's pointing.
zengtrade's ADX-based strategy uses exactly this pairing: it only takes a position when ADX confirms trend strength and the directional lines agree. The ADX floor is specifically what filters out the whipsaw trades that a plain moving-average crossover takes in a choppy market.
Educational content, not investment advice. zengtrade is paper-first and non-custodial.