The moment MACD crosses zero, which happens exactly when the fast moving average crosses the slow one.
A zero crossing is arithmetically identical to a moving-average-crossover between the 12 and 26 period averages. The MACD line is their difference, so it is zero when they are equal.
That makes it a slower and more conservative signal than a macd-signal-line cross, and traders often use the zero line as a regime filter: only take long signals while MACD is above zero.
Being equivalent to a crossover, it inherits every weakness of one, notably repeated flips in consolidation. Understanding that these are the same event under two names is a good antidote to stacking both on a chart and believing they confirm each other.
Original diagrams for the ideas on this page. Illustrative, not real market data.
MACD, signal line and histogram. The MACD line is the gap between a fast and a slow moving average, and the signal line is a smoothed copy of it. The bars show the distance between the two, and the circle marks where the faster line rises through the slower one.Fast and slow moving averages crossing. A moving average is the average of the last few closing prices, redrawn each period. An average over fewer periods turns sooner than one over many, so the two lines cross whenever the recent pace of the market changes.
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