A flag is a continuation pattern: a sharp move (the "pole"), followed by a tight, sideways-to-slightly-counter consolidation (the "flag"), before the trend resumes in the original direction. A bull flag points the resumption up; a bear flag points it down. It is the market catching its breath.

Why it forms

After a fast move, early buyers take profits and the price drifts or pauses. But if the trend is real, sellers can't push it far - the pullback is shallow and orderly. That tight consolidation is the flag. When price breaks out of it in the trend's direction, the pause is over and the next leg begins.

What makes it valid

The pole should be a genuine impulse move on real volume; the flag should be tight and low-volume (profit-taking, not distribution). A sloppy, wide, high-volume "flag" is not a flag - it's a reversal in disguise. Volume drying up during the pause and expanding on the breakout is the tell that separates the real thing from a coin flip.

A flag is the trend resting. In chop, everything looks like a flag - and none of them are.

The context trap

Flags work in trends and fail in ranges. Trade every "flag" in a choppy, mean-reverting tape and you'll get chopped up - the breakout is just noise reverting. The pattern is only as good as the regime it sits in, which is why structure and dealer positioning matter more than the shape itself. A pattern is a hypothesis, not a signal.