Web Typography

You are setting type for screens, not print. The goal is text that is legible (can you tell the letters apart), readable (is it comfortable to read at length), and clear in hierarchy (does the eye know where to go) — across every viewport, zoom level, and font preference a real user might have.

This skill encodes a small number of decisions that matter most, in the order you should make them. Work top-down: get the system right (scale, measure, rhythm) before reaching for clever features. Most "bad typography" on the web is not a missing OpenType flag — it's a body size that's too small, a measure that's too wide, line-height that's too tight, and a font that shifts the layout when it loads.

Provenance — principle, not property

This skill is an independent synthesis of widely-taught typographic principles, not a reproduction of anyone's writing, examples, or designs. Ideas are attributed to their lineage (e.g. measure from Bringhurst, Letter→Text→Grid from Lupton, the modular scale from Tim Brown) because crediting an idea is scholarship — but the expression and the web translation here are this skill's own. When you apply or extend it, do the same: express principles in your own words, credit the source of an idea where natural, and never copy a source's prose, sample layouts, or proprietary content. The shared knowledge is yours to use; any individual's expression is not.

The decision order

Make these decisions in sequence. Each one constrains the next.

1. Font choice — Default to a fast, good system stack unless the brand needs a web font. If you load a web font, plan its loading (step 6) at the same time.
2. Base size & measure — Body text ≥ 1rem (16px), line-length 45–75 characters (max-width: ~66ch). These two do more for readability than anything else.
3. Type scale — Pick one modular ratio and derive every size from it. Make it fluid with clamp(). Don't hand-pick random px values.
4. Vertical rhythm — Line-height ~1.5 for body, tighter (1.1–1.3) for large headings. Space paragraphs or indent them, never both.
5. Hierarchy & polish — Weight/size/space contrast, text-wrap: balance on headings and pretty on body, tracking on caps and display, OpenType features.
6. Loading & performance — font-display, preload the one critical font, self-host WOFF2, and metric-match the fallback so the page doesn't shift (CLS).
7. Accessibility pass — Contrast, zoom to 200%, the WCAG 1.4.12 text-spacing overrides, never disable zoom, never justify body text.

Non-negotiables (the rules that prevent the common failures)

These are the mistakes that show up again and again. Internalize the why so you can apply them in novel situations, not just copy them.

• Size body text in rem, never px. rem respects the user's browser font-size setting; px silently overrides an accessibility preference. Reserve px for hairline borders and genuinely fixed physical details.
• Line-height is unitless. line-height: 1.5 is inherited as a ratio, so each element recomputes from its own size. A fixed line-height: 24px inherits the computed pixel value and breaks on differently-sized children.
• Never size fonts in pure vw. Viewport units don't respond to zoom or user font-size — that fails WCAG 1.4.4. Always wrap fluid sizing in clamp() with a rem term: clamp(2rem, 1rem + 3vw, 4rem). The rem keeps zoom working.
• Constrain the measure. Lines longer than ~75 characters make the eye lose its place on the return sweep; shorter than ~45 gets choppy. max-width: 66ch on text containers is the single highest-leverage readability fix.
• Never justify body text on the web. CSS justification without sophisticated hyphenation opens "rivers" of whitespace. Left-align, ragged right.
• A web font must not shift the layout when it loads. Pair font-display with a metric-matched fallback (size-adjust + ascent/descent/line-gap-override) so swapping the real font in causes zero reflow. This is the fix for font-driven CLS.

Quick-start CSS

A sane, accessible baseline you can drop into almost any project. It uses a system font stack (zero download) and a fluid scale. Adapt the ratio and fonts to the brief.

:root {
  /* Fonts — system stack by default (instant, no CLS, native feel) */
  --font-sans: system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial,
               "Apple Color Emoji", "Segoe UI Emoji", sans-serif;
  --font-serif: Charter, "Bitstream Charter", "Sitka Text", Cambria, Georgia, serif;
  --font-mono: ui-monospace, "SF Mono", "Cascadia Code", Menlo, Consolas, monospace;

  /* Fluid type scale (≈ Major Third 1.25 at desktop). Generate real projects with Utopia.fyi */
  --step--1: clamp(0.833rem, 0.80rem + 0.17vw, 0.9rem);
  --step-0:  clamp(1rem,    0.95rem + 0.25vw, 1.125rem);   /* body */
  --step-1:  clamp(1.25rem, 1.15rem + 0.50vw, 1.5rem);
  --step-2:  clamp(1.563rem,1.40rem + 0.80vw, 1.953rem);
  --step-3:  clamp(1.953rem,1.70rem + 1.25vw, 2.441rem);
  --step-4:  clamp(2.441rem,2.00rem + 2.00vw, 3.052rem);

  --measure: 66ch;
}

html { font-size: 100%; -webkit-text-size-adjust: 100%; }

body {
  font-family: var(--font-sans);
  font-size: var(--step-0);
  line-height: 1.5;
  font-synthesis: none;            /* don't fake bold/italic */
  text-rendering: optimizeLegibility;
}

h1, h2, h3, h4 { line-height: 1.15; text-wrap: balance; }   /* tight + even line lengths */
h1 { font-size: var(--step-4); }
h2 { font-size: var(--step-3); }
h3 { font-size: var(--step-2); }
h4 { font-size: var(--step-1); }

p, li, blockquote { max-width: var(--measure); text-wrap: pretty; }  /* measure + no orphans */
p + p { margin-block-start: 1em; }                                   /* space, don't indent */

:is(h1, h2, h3, h4) + * { margin-block-start: 0.5em; }

/* Data/figures align in columns */
table, .tabular-nums { font-variant-numeric: tabular-nums; }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: .01ms !important; transition-duration: .01ms !important; }
}

A more complete, commented starter — including a metric-matched web-font example — is in assets/starter.css. Read it when scaffolding a project's type from scratch.

Reference files — read the one you need

Keep this file in context; pull a reference in when the task calls for it.

• references/decision-records.md — The distilled reasoning of the field: five meta-patterns (how typographers think) plus ADR-style decision records linking each rule to its rationale and the alternatives it rejects. Read this when you face a novel judgment the other files don't directly cover — the meta-patterns let you derive the right answer the way an expert would. Also the home of the "principle, not property" boundary.
• references/foundations.md — The classical principles (Lupton's Letter / Text / Grid, Bringhurst, Butterick) translated to the web: anatomy, measure, hierarchy, pairing, alignment. Read this when choosing/pairing fonts or when a layout "feels off" but no single rule is obviously broken.
• references/fluid-scale.md — Fluid type with clamp(), the clamp() math, modular-scale ratios, Utopia, container-query units (cqi) for component-level type. Read this when building or adjusting a type scale, or making type respond to a container rather than the viewport.
• references/font-loading.md — Web-font performance: font-display, preloading, self-hosting vs Google Fonts (GDPR), WOFF2, subsetting, unicode-range, variable fonts, and eliminating CLS with metric-matched fallbacks (size-adjust, *-override, Fontaine, next/font). Read this whenever a project loads a custom web font or has layout-shift / slow-text issues.
• references/accessibility.md — WCAG 2.2 for text: contrast ratios, resize to 200% (1.4.4), text-spacing overrides (1.4.12), zoom, dyslexia/readability, reduced motion. Read this before claiming type work is done, and any time the task mentions accessibility, a11y, contrast, or compliance.
• references/modern-css.md — Current CSS type features with browser-support status: text-wrap: balance/pretty, OpenType (font-variant-*, font-feature-settings), text-box-trim/text-box-edge, hanging-punctuation, initial-letter, font-relative units (lh, cap, ch, ic), line-clamp, color-mix for tints. Read this when reaching for a polish feature, and to check whether something needs progressive enhancement.

How to deliver

• When you change type, explain the decision, not just the code — "body bumped to 1.125rem and measure capped at 66ch so lines aren't 120 characters wide." Typography is judged by feel; tell the user what to look at.
• Prefer editing the project's existing tokens/scale over inventing a parallel one. If the project uses Tailwind, set the scale in theme.fontSize / CSS variables rather than scattering arbitrary values.
• Browser-support-sensitive features (flagged in modern-css.md) go in as progressive enhancement — the page must still read correctly without them.
• After non-trivial changes, do the accessibility pass (references/accessibility.md) before declaring done. Verify contrast and that the layout survives 200% zoom and the text-spacing overrides.