85% of the headlines I measured use it. Almost no beginner does. It is the smallest change with the biggest payoff.
If you gave me one measurement to guess whether a page was made by a designer or a beginner, I would ask for the headline's letter-spacing. In the dataset, 85% of measured headlines use negative letter-spacing. Among people learning design, almost none touch it. That gap is the single highest-leverage typographic habit I know.
Fonts are spaced for reading at body sizes. Blow a headline up to 60px or 120px and that same spacing looks loose, drifting, accidental. Pulling the tracking slightly negative closes the gaps so the word reads as one confident unit instead of a row of letters. The bigger the type, the more it needs it — which is exactly why the best sites, whose headlines are large, use it so consistently.
It is a feel, but there are ranges. Above roughly 40px, start around -0.5px to -1px and increase with size; a 100px display line can take -2px or more comfortably. Body text should almost never go negative — tightening small text hurts readability. The rule is simple: the larger and lighter the type, the more negative tracking helps; the smaller the type, the more it hurts.
On its own, tracking is a subtle change. But it compounds with the other two headline habits — light weight and large scale. Large, light and tightly tracked is the modern headline; and it is a completely different result from the beginner default of medium, bold and loosely spaced. Same words, same font, entirely different level of polish.
AI tools do not apply negative tracking unless asked. So ask: "H1 letter-spacing -1.5px." It is one clause, and it removes one of the most obvious tells of a generated page. Small detail, disproportionate payoff — my favorite kind.