Bollinger Bands plot a moving average (usually 20-period) with an upper and lower band set a number of standard deviations away (usually 2). Because the bands are built from standard deviation, they widen when volatility rises and contract when it falls — they breathe with the market.

The band-touch trap

The classic mistake: treating a touch of the upper band as "overbought, sell" and the lower band as "oversold, buy." In a strong trend, price can ride the upper band for a long time while climbing — shorting every touch gets you run over, exactly like the RSI overbought trap. A band touch means price is statistically stretched, not that it's about to reverse.

The squeeze

The genuinely useful signal is the squeeze: when the bands contract to an unusually narrow width, volatility has compressed — and volatility is mean-reverting, so a compression tends to precede an expansion. The squeeze doesn't tell you direction; it tells you a bigger move is coming. The breakout, on volume, points the way.

Bollinger Bands measure how stretched price is — not whether it's about to snap back.

Using them right

Bands are context, not a trigger. They tell you whether price is calm or stretched and whether volatility is coiling — useful for calibrating expectations and stop distance. Pair them with trend and structure; in a range they help fade extremes, in a trend they help you stay with the move. One input, never a system.