You only need to decide this once.

Rule of thumb#

• Long-form (>500 words): serif
• Short UI text, buttons, forms: sans-serif
• Code: monospace, never serif

That's the answer in 95% of cases.

Why serif for long-form#

Serifs provide horizontal cues at the top of letters that help the eye track along a line. In long paragraphs, that small assist accumulates into a real fatigue difference.

Research¹ shows serifs are slightly faster in continuous reading on print (>2400 dpi). On screen (96-220 dpi) the gap is smaller, but still there.

Why sans for UI#

UI text is short — buttons are 3 words, menu items are 1, error messages are a sentence. Sans-serif keeps more readable pixels at small sizes; serifs lose detail unevenly.

What about CJK#

CJK has no clean "serif vs sans-serif" mapping. The closest:

• Song / Ming ≈ serif (thin horizontal, thick vertical, sharp tips)
• Hei / Gothic ≈ sans-serif (uniform stroke weight)
• Kai / Cursive ≈ humanist serif (handwritten warmth)

Use	CN	Latin pair
Long-form	Song / Kai	EB Garamond / Newsreader
UI	Hei / Source	Inter / Helvetica
Headers	Hei bold	Sans bold

This site pairs LXGW WenKai (Kai-style) + Newsreader (humanist serif). They share humanist warmth. See CJK line breaks for more.

Don't#

• Set long-form in sans (unless you know readers will skim on mobile)
• Use serif for buttons (thin strokes break at small sizes)
• Mix more than three font families (visual noise)
• Use Comic Sans (unless your audience is five-year-olds)

Footnotes#

1. Karen Schriver, Dynamics in Document Design (1997) is the most-cited source. Hartley & Burnhill 1971 has the original data. Gaps fall in the 5-15% range, depending on font, lighting, and individual. ↩

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