Viewport widths: which devices are how wide?
Every common CSS viewport width, with the real phones, tablets, laptops and monitors behind it. Width is what decides whether your layout fits, so this is the number to design for.
Phones
Foldables, tablets and small windows
Laptops and monitors
Does your site fit?
Paste your address (or localhost:3000). doesitfit shows it on real screen sizes at once and tells you, bluntly, where it spills.
Free, no sign-up. Or ask Claude, ChatGPT or Codex to check it.
Guides that help
- Responsive breakpoints in 2026 — the widths that matterWhere 123 real phones, tablets, laptops and monitors land in CSS pixels, which responsive breakpoints actually matter in 2026, and which screens to test.Guides · 8 min read
- What is a viewport? CSS pixels vs screen resolutionA viewport is the area your page is laid out in, measured in CSS pixels, not screen pixels. See real numbers from iPhones and MacBooks, then check yours.Guides · 8 min read
- Tailwind breakpoints on real devices, from sm to 2xlWhich real phones, tablets, laptops and monitors land in Tailwind's sm, md, lg, xl and 2xl breakpoints, upright and sideways, plus the gotchas that bite.Guides · 8 min read