Tracking Is Size-Specific
SHOULD: Do not ship one `letter-spacing` for all sizes. Leave body near 0, tighten display type (~ -0.02em at 36px+), and give small caps/captions a small positive nudge. Prefer a variable font's optical-sizing axis (`font-optical-sizing: auto`) over a hardcoded value. This refines, not contradicts, "don't track body text".
Tighten letter-spacing as display type grows and leave body near zero — a single tracking value is wrong at some size
h1 { font-size: 48px; letter-spacing: -0.02em; }
.caption { font-size: 11px; letter-spacing: 0.04em; }
body { font-optical-sizing: auto; }Bad
Good
Why it matters
From the typography section of Emil Kowalski's apple-design skill, and it sits in DELIBERATE TENSION with content-ibelick-letter-spacing, which says never touch tracking unless asked. The corpus keeps both, because they are right about different sizes. ibelick's rule protects body text, where a face was hinted for reading and any manual tracking almost always makes it worse — that is the common case and the safe default.
Emil's rule is about the extremes a text-optimised face was never spaced for: at display sizes (36px and up) the designer-intended spacing reads too loose, the letters drift apart, and the headline stops cohering, so it wants slightly NEGATIVE tracking; at caption sizes (11–12px) it wants a touch POSITIVE to hold the glyphs apart. The honest reconciliation is that the best tool is not manual tracking at all but optical sizing — `font-optical-sizing: auto` on a variable font with an `opsz` axis corrects spacing, contrast and detail per size automatically, which is exactly what "type is designed with proper spacing" should mean end to end.
Reach for a manual `letter-spacing` step only when the face has no `opsz` axis. So: never randomly track body (that is ibelick's rule intact), do correct display and caption, and prefer `opsz` over a hardcoded value. Related: content-impeccable-type-scale-contrast, content-heading-size-descends, content-leading-tracks-size (its line-height counterpart).