Equal highs are two or more reversals that happened at practically the same price. The same applies to lows, mirrored. On a chart they look like a flat horizontal edge that price has bounced off several times.
Why "practically" rather than exactly
An exact match to the tick almost never occurs, and demanding one is pointless: the concept would never be found at all.
So extremes count as equal when the spread between them is small — by the standards of the instrument's own typical range, not in absolute terms. For a calm currency pair and a volatile coin, "practically the same price" means entirely different distances in points.
It follows that the set of equal levels depends on how wide a tolerance you chose. That is not a flaw in the markup but a consequence of the definition — as with almost everything else in structural markup.
Why they are considered meaningful
The reasoning runs like this: a prominent horizontal edge is visible to everyone, and protective orders naturally accumulate below or above it. The level becomes a place where many pending orders are concentrated.
Importantly, that is an argument about participant behaviour, not an observable fact. An exchange book does not show pending stop orders, and no chart can verify it. What is observable here is only the fact itself: price reversed at one level several times.
What happens to them next
Two outcomes, both ordinary.
The level is swept: price pierces the edge with a wick and comes back. The event has its own name — a liquidity sweep.
The level breaks: price goes beyond it and closes there. The equal extremes then stop being a level and become part of the movement's history.
Which of the two will happen does not follow from the markup in advance.
A common mistake
Treating equal highs as a sell signal and equal lows as a buy signal: "the level held three times, so it is strong." The number of touches guarantees nothing; in fact the customary structural argument runs the other way — the more prominent the edge, the likelier it is to be pierced.
Both versions are interpretations. The markup records only the level itself and what has already happened to it.