Butterick's Practical Typography

Typography is its own perceptual physics. Readability research predates computers by decades. Butterick’s guide is the most opinionated, practical distillation of it. One person’s durable principles, not a committee document.

The pages that matter

• Typography in ten minutes — the minimum viable knowledge
• Summary of key rules — the full checklist
• Line length — 45-90 characters per line
• Line spacing — 120-145% of font size
• Font size — never below 15-16px on screen
• Page layout — margins, whitespace, overall composition
• Headings — typographic hierarchy through size and weight
• Maxims of page layout — the principles behind the rules

Key ingredients for an agent

Line length, line spacing, font size, paragraph spacing, and heading hierarchy are mechanical — the pages above give specific numbers. Read the relevant page and apply.

Font choice is not mechanical. It’s the difference between a correct page and a page with character. System fonts are safe. A well-chosen web font is a voice. This is the one decision the agent should not make alone — ask the user what tone the page should carry, then propose options. Butterick’s font recommendations are a good starting point for the conversation.

Reference implementations

• NetNewsWire (MIT) — reader typography: system fonts, proper line height, comfortable reading width, low-noise hierarchy.