Three parts
MACD is the difference between two EMAs (usually 12 and 26). The 'MACD line' is that difference; the 'signal line' is a 9-EMA of it; the 'histogram' is the gap between the two. It's momentum built out of moving averages, so it inherits their lag.
Common readings: MACD crossing above its signal line is a bullish nudge; crossing below, bearish. The histogram shrinking toward zero warns momentum is fading before the cross even happens.
Above/below zero
Whether MACD is above or below the zero line tells you which EMA is on top — a rough trend filter. MACD crosses far from zero carry more weight than the constant chop that happens near it in a range.
Reading the three parts together
MACD is one picture with three pieces — read them as a sentence:
- MACD line vs signal line — the cross is the momentum-shift headline.
- Histogram — the gap between them; shrinking bars warn momentum is fading before the cross.
- Zero line — above it the fast EMA leads (uptrend side), below it the slow one leads.
Use the zero line as a filter
Crosses that happen while MACD is well above (or below) zero align with the trend and carry more weight; crosses hugging the zero line in a range are mostly noise. Because MACD is built from lagging averages, treat the histogram's rate-of-change as the earliest tell and confirm with structure — never trade the cross alone.