codex-typography

name	codex-typography
description	The single most important text rule in Codex — every piece of text must use exactly ONE of the 9 canonical text styles (Heading 1–4, Body, Small, Figure caption, Block quote, Cite). Each style is a fixed combination of font-family, font-size, font-weight, and line-height; never invent font combinations or mix tokens across styles. Use whenever you add or style any text — a heading, paragraph, label, caption, or quote.
license	MIT

Codex typography

The rule: every piece of text uses exactly one of 9 canonical text styles. Each style is a fixed combination of four tokens — font-family, font-size, font-weight, line-height. Pick a whole style; never mix tokens across styles (e.g. body size with a heading weight, or a heading size with body line-height). Agents drift here constantly — don't.

The easiest way to comply is to write plain semantic HTML (h1–h4, p, small, blockquote, cite, figcaption) and add no font CSS — the element already carries the right style.

The 9 text styles

Each style is exactly these four tokens. Source: Codex typography → Use of styles.

Style	HTML	Tokens (family · size · weight · line-height)
Heading 1	h1	--font-family-serif · --font-size-xxx-large · --font-weight-normal · --line-height-xxx-large
Heading 2	h2	--font-family-serif · --font-size-xx-large · --font-weight-normal · --line-height-xx-large
Heading 3	h3	--font-family-base · --font-size-x-large · --font-weight-bold · --line-height-x-large
Heading 4	h4	--font-family-base · --font-size-large · --font-weight-bold · --line-height-large
Body	p	--font-family-base · --font-size-medium · --font-weight-normal · --line-height-medium
Small	small	--font-family-base · --font-size-small · --font-weight-normal · --line-height-small
Figure caption	figcaption	--font-family-base · --font-size-small · --font-weight-normal · --line-height-small
Block quote	blockquote	--font-family-serif · --font-size-medium · --font-weight-normal · --line-height-medium
Cite	cite	--font-family-base · --font-size-small · --font-weight-normal · --line-height-small

Notes:

• The scale stops at Heading 4. There is no official Heading 5/6 — restructure the content rather than nesting deeper.
• Small, Figure caption, and Cite share the same four tokens; they're distinct semantically (use the matching element), not visually.
• Code is separate from these prose styles: use --font-family-monospace (the code / kbd / samp / pre elements already do).

If you can't use the semantic element

When you genuinely need a class (e.g. a non-heading element that should read as a heading), copy a whole style row — all four tokens — rather than picking sizes ad hoc:

.section-title {
  font-family: var(--font-family-serif);
  font-size: var(--font-size-xx-large);
  font-weight: var(--font-weight-normal);
  line-height: var(--line-height-xx-large);
}

What the rule already gives you — and what it doesn't

Following a style means font family and line-height are handled for you (the --font-family-* tokens are system-font stacks, and each size is paired with its matching --line-height-*). You still control:

• Line length — keep prose to ~≤ 75 characters per line.
• Dynamic text — text length varies across languages; don't assume a fixed length (let containers expand, shrink long content, clip only when nothing is lost).
• Contrast — a colour concern, not a type one; meet 4.5:1 (see codex-style-guide → accessibility).

Full token tables

This skill is about the rule. For the exhaustive token value tables (every --font-size-*, --font-weight-*, --line-height-* with px approximations) see codex-tokens → typography.

Inside ProtoWiki

src/styles/global.css maps h1–h6, p, small, blockquote, cite, figcaption, code/kbd/samp, pre, and related elements to the 9 styles. Prefer plain semantic markup in prototypes — that's how you get the canonical typography for free.

Reader-style underlines on primary titles use mw-first-heading (PlainWrapper, ArticleRenderer's .article-content, .mw-parser-output); that class only adds the separator — the size comes from h1 + the Heading 1 style.