Responsive Layout Breaks Below 375px Screen Width
Your application's layout breaks on very small screens (below 375px width), even though it looks fine on standard mobile sizes. Elements overflow horizontally, text gets cut off, buttons become untappable, and the page requires horizontal scrolling to use.
This affects users with older or smaller phones (iPhone SE, Galaxy A series), users who have increased their system font size, and users viewing your app in split-screen mode on tablets. These are real users who are completely locked out of your app.
Claude Code typically generates responsive CSS targeting common breakpoints (768px, 640px) but doesn't account for screens smaller than 375px, where fixed pixel widths, min-width declarations, and padding cause layout overflow.
Error Messages You Might See
Common Causes
- min-width on containers — CSS rules like min-width: 375px or min-width: 320px prevent the layout from shrinking further
- Fixed pixel widths — Elements have width: 360px or similar fixed values that can't adapt to smaller screens
- Horizontal padding overflow — Container padding (e.g., px-8 / 32px on each side) consumes too much of the narrow viewport
- Flexbox not wrapping — Row layouts with flex-nowrap force elements side by side when they should stack
- Media queries start too high — The smallest breakpoint is 640px, with no styles for screens below that
How to Fix It
- Design mobile-first — Write base styles for the smallest screen, then add complexity with min-width media queries
- Replace fixed widths with percentages or max-width — Use width: 100% or max-width: 100% instead of pixel values
- Reduce padding on small screens — Use responsive padding like p-3 sm:p-6 to reduce spacing on narrow viewports
- Test at 320px width — Use Chrome DevTools responsive mode set to 320px to find overflow issues
- Add overflow-x: hidden cautiously — Only on the body element as a safety net, not as a fix for individual layout issues
- Use clamp() for font sizes — Replace fixed font sizes with clamp(14px, 4vw, 18px) for fluid typography
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Get HelpFrequently Asked Questions
What is the smallest screen width I should support?
Design for 320px as the minimum. This covers iPhone SE, older Android phones, and split-screen tablet usage. Test at 320px during development to catch overflow issues early.
How do I find what's causing horizontal scroll?
In Chrome DevTools, add a temporary style: * { outline: 1px solid red; } to see every element's boundaries. The element extending beyond the viewport edge is your culprit.