What MACD Actually Is
MACD ("moving average convergence divergence") is a momentum indicator built from two exponential moving averages of price and a signal line on top of that. The MACD line is the 12-period EMA minus the 26-period EMA. The signal line is the 9-period EMA of the MACD line. The histogram is MACD minus signal. Those three numbers, plotted under the price chart, tell you whether momentum is accelerating, decelerating, or reversing.
Reading the Three Components
MACD line above zero: short-term EMA is above long-term EMA, meaning recent price is above the medium-term average. The market is in an uptrend on this timeframe. MACD below zero: opposite ? downtrend in force. The further MACD is from zero, the stronger the trend.
Signal line crossovers are the classic MACD trading signal. MACD crossing above the signal line is a bullish crossover; MACD crossing below is bearish. These work best when they happen on the same side as the trend (bullish crossover above zero, bearish below zero).
Histogram shows the gap between MACD and signal. Growing positive bars mean the bullish momentum is accelerating. Shrinking positive bars mean momentum is fading ? a possible warning before a crossover.
MACD Divergence
The most useful MACD signal is divergence. Bullish divergence: price makes a lower low but MACD makes a higher low. The selling is losing steam even though prices are still falling ? often a precursor to a bounce. Bearish divergence: price makes a higher high but MACD makes a lower high. Buyers are exhausted at the new peak.
Divergence is a warning, not a trigger. Wait for a confirmation move ? a signal-line crossover in the divergence direction, or a break of a recent swing point.
Practical Settings
The default 12/26/9 is what most traders watch, so the signals it generates have real impact. Faster settings (5/13/4) for short timeframes; slower (24/52/9) for weekly charts. Resist the urge to over-tune.
Where MACD Fails
In ranging markets, MACD whipsaws around zero generating false crossovers. It works best on trending instruments and timeframes ? index ETFs on daily charts, large-cap stocks on weekly, futures on 4H. On choppy small-caps it produces more noise than signal. Always check whether the market is actually trending before trusting MACD.