Kerning, tracking, and leading are the three core spacing controls in typography — kerning adjusts the space between two specific letters, tracking adjusts the overall spacing across a whole word or line uniformly, and leading (rhymes with "sledding") adjusts the vertical space between lines of text. They're easy to confuse because they all deal with space, but each solves a different, specific problem, and getting one right doesn't fix the other two.

Space the Eye Never Consciously Measures

Readers never consciously notice correct spacing, but they register incorrect spacing almost immediately, because the eye relies on consistent, predictable gaps to segment text into words and lines without effort. A single mismatched gap between two letters, or one cramped line among generously spaced ones, disrupts that segmentation just enough to force a small, unconscious re-read, which is why bad spacing feels like "something is off" long before anyone identifies what.

In Product Design

Kerning problems typically live in large display type, where letter pairs like "AV" or "To" can visually gap or collide unless manually adjusted, since automatic kerning tables aren't tuned for every size. Tracking is used deliberately in interface design: slightly increased tracking on all-caps labels and button text improves their legibility, since capital letters set at normal tracking can feel cramped. Leading is the workhorse of body copy legibility, with roughly 1.4 to 1.6 times the font size being the common comfortable range for reading.

  • All-caps navigation labels set at normal tracking, making the capital letters feel visually cramped and harder to scan than lowercase text would be
  • A large display headline where letter pairs create awkward, inconsistent gaps that weren't present at smaller sizes
  • Body paragraphs with tight, single-spaced leading that makes it easy to lose your place moving from the end of one line to the start of the next
  • Justified text with no adjustment to word spacing, producing uneven, distracting gaps running down the page

Each of these is a spacing problem with a specific fix, wider tracking, manual kerning, more generous leading, but they're often misdiagnosed as "the font looks wrong" when the font itself was never actually the issue.

How to Apply It

Increase tracking slightly on all-caps and small text, since capitals and small sizes both read more comfortably with a bit more room. Manually check and adjust kerning on anything set large enough that individual letter pairs are clearly visible, like display headlines and logotypes. Set leading generously for body copy, and tighten it deliberately, never by default, for large display text where lines sit close enough that extra space would look like a mistake.

Why It Matters

Spacing is one of the most common places where a design that "looks fine" at a glance turns out to be quietly harder to read than it should be, because none of these issues are dramatic enough to name individually. The cumulative effect, though, is real reading fatigue, especially at length. A fast test: read three paragraphs at actual size and normal reading distance. If your eyes feel like they're working, spacing is the first place to check before touching the typeface itself.