UI Typography Skill

Attribution

These rules are distilled from Matthew Butterick's Practical Typography (https://practicaltypography.com). Butterick is a typographer, writer, and type designer whose work bridges professional typography and everyday digital writing. Thank you, Matthew, for making this knowledge accessible and encyclopedic. If you find this skill valuable, consider supporting his work directly.

Mode of Operation

These are permanent rules — not trends, not opinions. They come from centuries of typographic practice, validated by how the human eye reads. They do not go out of style.

ENFORCEMENT (default): When generating ANY UI with visible text, apply every rule automatically. Use correct HTML entities, proper CSS. Do not ask permission. Do not explain. Just produce correct typography.

AUDIT: When reviewing existing code or design, identify violations and provide before/after fixes.

Reference files (read when generating CSS or looking up entities):

references/css-templates.md — Full CSS baseline template, responsive patterns, OpenType features
references/html-entities.md — Complete entity table with all characters and codes

Characters

Quotes and Apostrophes — Always Curly

Straight quotes are typewriter artifacts. Use “ ” for double, ‘ ’ for single.

Apostrophes always point down — identical to closing single quote ’. Smart-quote engines wrongly insert opening quotes before decade abbreviations ('70s) and word-initial contractions ('n'). Fix with explicit ’.

The <q> tag auto-applies curly quotes when <html lang="en"> is set.

Hawaiian okina points upward — it's a letter, not an apostrophe. Use opening single quote or anglicize.

JSX/React Implementation Warning

Unicode escape sequences (\u2019, \u201C, etc.) do NOT work in JSX text content. They render as literal characters — the user sees \u2019 instead of a curly apostrophe. This is because JSX text between tags is treated as string literals by the transpiler, not as JavaScript expressions.

What fails:

{/* WRONG — renders literally as \u2019 */}
<p>Don\u2019t do this</p>

What works (pick one):

Actual UTF-8 characters (preferred): Paste the real character directly into the source file.
```
Don\u2019t do this {/* This is the actual curly apostrophe character U+2019 */}
```
JSX expression with string literal: Wrap in curly braces so the JS engine interprets the escape.
```
Don{'\u2019'}t do this
```
HTML entity (HTML files only): Use ’ — but this does NOT work in JSX/React.

For bulk fixes via CLI, use sed with raw UTF-8 bytes (not escape sequences):

CURLY=$(printf '\xe2\x80\x99')  # U+2019 RIGHT SINGLE QUOTATION MARK
sed -i '' "s/don't/don${CURLY}t/g" file.tsx

In JavaScript data arrays and string literals, \u2019 works correctly because the JS engine processes the escape. The bug only affects JSX text content between tags.

Dashes and Hyphens — Three Distinct Characters

| Character | HTML | Use | |-----------|------|-----| | - (hyphen) | - | Compound words (cost-effective), line breaks | | – (en dash) | – | Ranges (1–10), connections (Sarbanes–Oxley Act) | | — (em dash) | — | Sentence breaks—like this |

Never approximate with -- or ---. If you open with "from", pair with "to" not en dash. Hyphen for compound names (marriage); en dash for joint authorship. Em dash typically flush; add   if crushed. No slash where en dash belongs. Hyphenate phrasal adjectives (five-dollar bills). No hyphen after -ly adverbs.

Ellipses — One Character

Use … (…), not three periods. Spaces before and after; use   on the text-adjacent side. For interrupted dialogue, prefer em dash over ellipsis.

Math and Measurement

Use × for multiplication, − for subtraction. Use + and = from keyboard. En dash is acceptable as simple minus. Dimensions: 8.5″ × 14″ uses ×.

Foot and inch marks — the ONE exception to curly quotes. Must be STRAIGHT: ' for foot, " for inch. Use   between values: 6' 10".

Trademark and Copyright

Paragraph and Section Marks

§ (§) and ¶ (¶) always followed by  : § 1782. Spell out at sentence start. Double for plurals: §§.

Accented Characters

Proper names: accents are MANDATORY (François Truffaut, Plácido Domingo). Loanwords: check dictionary — some naturalized (naive), some not (cause célèbre).

Other Punctuation

Semicolons join independent clauses. Colons introduce completion. Don't mix them
Question marks: underused — simplify topic sentences with them
Exclamation points: overused — budget ONE per long document. Never multiple in a row
Ampersands: correct in proper names only. Write "and" in body text
Parentheses/brackets: do NOT adopt formatting of surrounded material
Emoticons/emoji: OK in email/Slack. Never in formal documents or professional UI copy

Spacing

One Space After Punctuation — Always

Exactly one space after any punctuation. Never two. Not debatable. Two spaces create rivers and disrupt text balance. The period already contains visual white space.

Nonbreaking Spaces

  prevents line break. Use before numeric refs (§ 42, Fig. 3), after © (© 2025), after honorifics (Dr. Smith), between foot/inch values.

White-Space Characters

| Need | Tool | |------|------| | Space between words | One word space (spacebar) | | Prevent line break |   | | New line, same paragraph |   | | New paragraph |  tags | | New page (print) | page-break-before: always | | Suggest hyphenation point |  |

Never hold spacebar. Never double carriage returns for spacing. Never tabs for indentation in output. HTML collapses all whitespace to single space (except  ).

Text Formatting

Bold and Italic

Rule 1: Bold OR italic. Mutually exclusive. Never combine. Rule 2: Use as little as possible. If everything is emphasized, nothing is.

Serif: italic for gentle, bold for strong. Sans serif: bold only — italic sans barely stands out. Never bold entire paragraphs. Never use quotation marks for emphasis.

Underlining — Never

Never underline in a document or UI. Typewriter workaround. Use bold or italic. For web links, use subtle styling: text-decoration-thickness: 1px; text-underline-offset: 2px.

All Caps — Less Than One Line, Always Letterspaced

Caps are harder to read (homogeneous rectangles vs varied lowercase contour). Suitable for short headings, labels, captions. ALWAYS add 5–12% letterspacing. ALWAYS ensure kerning is on. NEVER capitalize whole paragraphs. letter-spacing: 0.06em in CSS.

Small Caps — Real Only

Never fake (scaled-down regular caps). Use font-variant-caps: small-caps with fonts that have real small caps (OpenType smcp). System fonts lack them. Add letterspacing + kerning.

Point Size

Print: 10–12pt. Web: 15–25px. The 12pt default is a typewriter relic. Half-point differences matter. Use smallest increment for emphasis. Use clamp() for fluid web sizing.

Letterspacing

5–12% extra on ALL CAPS and small caps. Nothing on lowercase. Never spread so far apart that letters could fit in the gaps. CSS: letter-spacing: 0.05em to 0.12em.

Kerning — Always On

No exceptions. font-feature-settings: "kern" 1; text-rendering: optimizeLegibility;

Ligatures

Mandatory only when fi/fl visually collide. Check bold and italic too. Otherwise optional. CSS: font-feature-settings: "liga" 1.

Alternate Figures

Tabular ("tnum") for data tables. Oldstyle ("onum") for body text. Default figures are fine for most uses. font-variant-numeric: tabular-nums lining-nums for numeric tables.

Font Selection

No goofy fonts (novelty, script, handwriting, circus) in professional work
No monospaced for body text — code only (and Courier is the worst monospaced)
Print body: strongly prefer serif
Web body: serif or sans both fine on modern screens
Metrics spacing in InDesign, never optical (optical mangles kerning)

Mixing Fonts

Max 2 fonts. Each gets a consistent role. Can mix serif+serif or sans+sans. Rarely mix within a paragraph. Lower contrast often more effective than high contrast.

Page Layout

Body Text First

Set body text BEFORE anything else. Four decisions determine everything: font, point size, line spacing, line length. All other elements calibrate against these.

Line Length — 45–90 Characters

The #1 readability factor designers get wrong. The #1 flaw in responsive web layouts. Measure in characters, not inches. Alphabet test: fit 2–3 lowercase alphabets per line. CSS: max-width: 65ch on text containers.

Line Spacing — 120–145% of Point Size

line-height: 1.2 to 1.45. Single-spaced (~117%) is too tight. Double (~233%) is too loose. Word processor "Single" and "Double" both miss the optimal range.

Page Margins

One inch is not enough for proportional fonts. Print: 1.5–2.0″ at 12pt. Web: max-width on text containers plus padding. Don't fear white space — generous margins look professional.

Text Alignment

Left-align for web (default). Justified requires hyphens: auto — browser engines are crude. Centered: sparingly, only for short titles (< 1 line). Never center whole text blocks.

Paragraph Separation — Indent OR Space, Never Both

First-line indent: 1–4× point size. text-indent: 1.5em. Optional on first paragraph. Space between: 50–100% of font size. margin-bottom: 0.75em. Never double   tags.

Headings — Max 3 Levels

Don't all-caps headings (unless very short + letterspaced)
Don't underline headings
Don't center headings (rare exceptions)
Emphasize with space above and below — subtle and effective
Use bold, not italic — stands out better
Smallest point-size increment needed (body 11pt → heading 13pt, not 18pt)
hyphens: none on headings
Space above > space below (heading relates to text that follows)
Keep heading with next paragraph (page-break-after: avoid)
Tiered numbers (1.1, 2.1) over roman numerals (I.A.1.a.i)

Block Quotations

Reduce size + line spacing slightly. Indent 2–5em. No quotation marks (indent signals the quote). Keep line length readable. Use sparingly — long block quotes signal lazy writing.

Lists

Semantic markup (<ul>, <ol>), never manual bullets. Prefer hollow bullets. Asterisks are too small for bullets. Don't over-indent.

Tables — Remove Borders, Add Padding

Data creates an implied grid. Borders add clutter. Keep only thin rule under header row. padding: 0.5em 1em. Tabular figures for numeric columns. Right-align numbers.

Rules and Borders

Try space above and below first. Border thickness: 0.5–1pt. No patterned borders. Thick lines are chartjunk.

Flow Control

Widows (last line alone at top of page) and orphans (first line alone at bottom). CSS print: orphans: 2; widows: 2. Headings: page-break-after: avoid. Soft hyphens  for words that confuse hyphenation engines.

Columns and Grids

Print columns: 2–3 on letter paper, never 4. Web columns: awkward (indefinite bottom edge). Grids guide, not guarantee — simpler grids enforce more consistency. Aligning ugly to a grid still produces ugly.

Responsive Web Typography

The rules don't change with screen size. Same line length, line spacing, hierarchy.

Scale font-size and container width together
Always max-width on text containers — never edge-to-edge text
Don't use ch unit for exact measurement (only measures zero width)
clamp() for fluid scaling: font-size: clamp(16px, 2.5vw, 20px)
Mobile minimum: padding: 0 1rem on text containers
The common failure: images/nav scale carefully, body text ignored

Screen Considerations

Modern screens render type nearly as well as print. "Sans serif for screens" was true for 72dpi and is now obsolete. Serif fonts work fine on modern screens. Dark mode: reduce weight slightly. Test on macOS and Windows (antialiasing differs).

Maxims of Page Layout

Body text first — its 4 properties determine everything
Foreground vs background — don't let chrome upstage body text
Smallest visible increments — half-points matter
When in doubt, try both — make samples, don't theorize
Consistency — same things look the same
Relate new to existing — each element constrains the next
Keep it simple — 3 colors and 5 fonts? Think again
Imitate what you like — emulate good typography from the wild

UI Typography Skill

Attribution

Mode of Operation

These are permanent rules — not trends, not opinions. They come from centuries of typographic practice, validated by how the human eye reads. They do not go out of style.

AUDIT: When reviewing existing code or design, identify violations and provide before/after fixes.

Reference files (read when generating CSS or looking up entities):

references/css-templates.md — Full CSS baseline template, responsive patterns, OpenType features
references/html-entities.md — Complete entity table with all characters and codes

Characters

Quotes and Apostrophes — Always Curly

Straight quotes are typewriter artifacts. Use “ ” for double, ‘ ’ for single.

The <q> tag auto-applies curly quotes when <html lang="en"> is set.

Hawaiian okina points upward — it's a letter, not an apostrophe. Use opening single quote or anglicize.

JSX/React Implementation Warning

What fails:

{/* WRONG — renders literally as \u2019 */}
<p>Don\u2019t do this</p>

What works (pick one):

Actual UTF-8 characters (preferred): Paste the real character directly into the source file.
```
Don\u2019t do this {/* This is the actual curly apostrophe character U+2019 */}
```
JSX expression with string literal: Wrap in curly braces so the JS engine interprets the escape.
```
Don{'\u2019'}t do this
```
HTML entity (HTML files only): Use ’ — but this does NOT work in JSX/React.

For bulk fixes via CLI, use sed with raw UTF-8 bytes (not escape sequences):

CURLY=$(printf '\xe2\x80\x99')  # U+2019 RIGHT SINGLE QUOTATION MARK
sed -i '' "s/don't/don${CURLY}t/g" file.tsx

In JavaScript data arrays and string literals, \u2019 works correctly because the JS engine processes the escape. The bug only affects JSX text content between tags.

Dashes and Hyphens — Three Distinct Characters

Ellipses — One Character

Use … (…), not three periods. Spaces before and after; use   on the text-adjacent side. For interrupted dialogue, prefer em dash over ellipsis.

Math and Measurement

Use × for multiplication, − for subtraction. Use + and = from keyboard. En dash is acceptable as simple minus. Dimensions: 8.5″ × 14″ uses ×.

Foot and inch marks — the ONE exception to curly quotes. Must be STRAIGHT: ' for foot, " for inch. Use   between values: 6' 10".

Trademark and Copyright

Paragraph and Section Marks

§ (§) and ¶ (¶) always followed by  : § 1782. Spell out at sentence start. Double for plurals: §§.

Accented Characters

Proper names: accents are MANDATORY (François Truffaut, Plácido Domingo). Loanwords: check dictionary — some naturalized (naive), some not (cause célèbre).

Other Punctuation

Semicolons join independent clauses. Colons introduce completion. Don't mix them
Question marks: underused — simplify topic sentences with them
Exclamation points: overused — budget ONE per long document. Never multiple in a row
Ampersands: correct in proper names only. Write "and" in body text
Parentheses/brackets: do NOT adopt formatting of surrounded material
Emoticons/emoji: OK in email/Slack. Never in formal documents or professional UI copy

Spacing

One Space After Punctuation — Always

Exactly one space after any punctuation. Never two. Not debatable. Two spaces create rivers and disrupt text balance. The period already contains visual white space.

Nonbreaking Spaces

  prevents line break. Use before numeric refs (§ 42, Fig. 3), after © (© 2025), after honorifics (Dr. Smith), between foot/inch values.

White-Space Characters

Never hold spacebar. Never double carriage returns for spacing. Never tabs for indentation in output. HTML collapses all whitespace to single space (except  ).

Text Formatting

Bold and Italic

Rule 1: Bold OR italic. Mutually exclusive. Never combine. Rule 2: Use as little as possible. If everything is emphasized, nothing is.

Serif: italic for gentle, bold for strong. Sans serif: bold only — italic sans barely stands out. Never bold entire paragraphs. Never use quotation marks for emphasis.

Underlining — Never

Never underline in a document or UI. Typewriter workaround. Use bold or italic. For web links, use subtle styling: text-decoration-thickness: 1px; text-underline-offset: 2px.

All Caps — Less Than One Line, Always Letterspaced

Small Caps — Real Only

Never fake (scaled-down regular caps). Use font-variant-caps: small-caps with fonts that have real small caps (OpenType smcp). System fonts lack them. Add letterspacing + kerning.

Point Size

Print: 10–12pt. Web: 15–25px. The 12pt default is a typewriter relic. Half-point differences matter. Use smallest increment for emphasis. Use clamp() for fluid web sizing.

Letterspacing

5–12% extra on ALL CAPS and small caps. Nothing on lowercase. Never spread so far apart that letters could fit in the gaps. CSS: letter-spacing: 0.05em to 0.12em.

Kerning — Always On

No exceptions. font-feature-settings: "kern" 1; text-rendering: optimizeLegibility;

Ligatures

Mandatory only when fi/fl visually collide. Check bold and italic too. Otherwise optional. CSS: font-feature-settings: "liga" 1.

Alternate Figures

Tabular ("tnum") for data tables. Oldstyle ("onum") for body text. Default figures are fine for most uses. font-variant-numeric: tabular-nums lining-nums for numeric tables.

Font Selection

No goofy fonts (novelty, script, handwriting, circus) in professional work
No monospaced for body text — code only (and Courier is the worst monospaced)
Print body: strongly prefer serif
Web body: serif or sans both fine on modern screens
Metrics spacing in InDesign, never optical (optical mangles kerning)

Mixing Fonts

Max 2 fonts. Each gets a consistent role. Can mix serif+serif or sans+sans. Rarely mix within a paragraph. Lower contrast often more effective than high contrast.

Page Layout

Body Text First

Set body text BEFORE anything else. Four decisions determine everything: font, point size, line spacing, line length. All other elements calibrate against these.

Line Length — 45–90 Characters

Line Spacing — 120–145% of Point Size

line-height: 1.2 to 1.45. Single-spaced (~117%) is too tight. Double (~233%) is too loose. Word processor "Single" and "Double" both miss the optimal range.

Page Margins

One inch is not enough for proportional fonts. Print: 1.5–2.0″ at 12pt. Web: max-width on text containers plus padding. Don't fear white space — generous margins look professional.

Text Alignment

Left-align for web (default). Justified requires hyphens: auto — browser engines are crude. Centered: sparingly, only for short titles (< 1 line). Never center whole text blocks.

Paragraph Separation — Indent OR Space, Never Both

First-line indent: 1–4× point size. text-indent: 1.5em. Optional on first paragraph. Space between: 50–100% of font size. margin-bottom: 0.75em. Never double   tags.

Headings — Max 3 Levels

Don't all-caps headings (unless very short + letterspaced)
Don't underline headings
Don't center headings (rare exceptions)
Emphasize with space above and below — subtle and effective
Use bold, not italic — stands out better
Smallest point-size increment needed (body 11pt → heading 13pt, not 18pt)
hyphens: none on headings
Space above > space below (heading relates to text that follows)
Keep heading with next paragraph (page-break-after: avoid)
Tiered numbers (1.1, 2.1) over roman numerals (I.A.1.a.i)

Block Quotations

Reduce size + line spacing slightly. Indent 2–5em. No quotation marks (indent signals the quote). Keep line length readable. Use sparingly — long block quotes signal lazy writing.

Lists

Semantic markup (<ul>, <ol>), never manual bullets. Prefer hollow bullets. Asterisks are too small for bullets. Don't over-indent.

Tables — Remove Borders, Add Padding

Data creates an implied grid. Borders add clutter. Keep only thin rule under header row. padding: 0.5em 1em. Tabular figures for numeric columns. Right-align numbers.

Rules and Borders

Try space above and below first. Border thickness: 0.5–1pt. No patterned borders. Thick lines are chartjunk.

Flow Control

Columns and Grids

Responsive Web Typography

The rules don't change with screen size. Same line length, line spacing, hierarchy.

Scale font-size and container width together
Always max-width on text containers — never edge-to-edge text
Don't use ch unit for exact measurement (only measures zero width)
clamp() for fluid scaling: font-size: clamp(16px, 2.5vw, 20px)
Mobile minimum: padding: 0 1rem on text containers
The common failure: images/nav scale carefully, body text ignored

Screen Considerations

Maxims of Page Layout

Body text first — its 4 properties determine everything
Foreground vs background — don't let chrome upstage body text
Smallest visible increments — half-points matter
When in doubt, try both — make samples, don't theorize
Consistency — same things look the same
Relate new to existing — each element constrains the next
Keep it simple — 3 colors and 5 fonts? Think again
Imitate what you like — emulate good typography from the wild

Adoption

seikaikyo/ui-typography

$ install --global

Security Scan Results

SKILL.md

UI Typography Skill

Attribution

Mode of Operation

Characters

Quotes and Apostrophes — Always Curly

JSX/React Implementation Warning

Dashes and Hyphens — Three Distinct Characters

Ellipses — One Character

Math and Measurement

Trademark and Copyright

Paragraph and Section Marks

Accented Characters

Other Punctuation

Spacing

One Space After Punctuation — Always

Nonbreaking Spaces

White-Space Characters

Text Formatting

Bold and Italic

Underlining — Never

All Caps — Less Than One Line, Always Letterspaced

Small Caps — Real Only

Point Size

Letterspacing

Kerning — Always On

Ligatures

Alternate Figures

Font Selection

Mixing Fonts

Page Layout

Body Text First

Line Length — 45–90 Characters

Line Spacing — 120–145% of Point Size

Page Margins

Text Alignment

Paragraph Separation — Indent OR Space, Never Both

Headings — Max 3 Levels

Block Quotations

Lists

Tables — Remove Borders, Add Padding

Rules and Borders

Flow Control

Columns and Grids

Responsive Web Typography

Screen Considerations

Maxims of Page Layout

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seikaikyo/ui-typography

$ install --global

Security Scan Results

SKILL.md

UI Typography Skill

Attribution

Mode of Operation

Characters

Quotes and Apostrophes — Always Curly

JSX/React Implementation Warning

Dashes and Hyphens — Three Distinct Characters

Ellipses — One Character

Math and Measurement

Trademark and Copyright

Paragraph and Section Marks

Accented Characters

Other Punctuation

Spacing

One Space After Punctuation — Always

Nonbreaking Spaces

White-Space Characters

Text Formatting

Bold and Italic

Underlining — Never