Mobile UX Checklist: Viewport, Tap Targets & Font Size
The three mobile UX basics that break launches most often — a missing viewport tag, tap targets too small to hit, and body text too small to read.
Most first visits are on a phone
A site built and reviewed on a laptop can look finished while being genuinely broken on the device most visitors will actually use. Mobile UX problems are also unusually invisible to the person who built the page — you know where every button is, so you never notice it's two millimetres too small to hit reliably with a thumb.
Three checks, most of the damage
The mobile dimension is deliberately narrow: a viewport meta tag, tap target size, and font size. That's not because mobile UX is simple — it's because these three are the specific failures that break a page outright rather than just looking slightly off, and they're the ones a rules-based check can verify reliably without guessing at subjective layout quality.
Common mistakes we see
- No viewport meta tag. Without it, mobile browsers render the page at desktop width and shrink it to fit — every other mobile fix is pointless until this one exists.
- Tap targets sized for a mouse cursor. Buttons and links built at desktop-click sizes, with no extra padding for a fingertip, especially when several sit close together — a mis-tap on the wrong link is a lost visitor.
- Body text under 16px. Readable on a laptop at arm's length, genuinely small on a phone screen held closer — and it forces a visitor to pinch-zoom, which most just won't bother doing.
- Desktop-only navigation patterns. Hover-triggered menus or wide multi-column layouts that don't collapse, forcing horizontal scrolling on a narrow screen.
How to check it yourself
Open the page on an actual phone, not a resized browser window — the two behave differently in ways that matter here. Try to tap every link and button in your main navigation and your primary CTA using only your thumb, without zooming in first. If you catch yourself pinching to read the body copy, your font size is too small before you ever run a formal check.
What LaunchGraded actually checks here
These are scored automatically as part of the free scan — the list above is reasoning and context, this is the exact, deterministic checklist behind the score.