Free Responsive Design Checker

It loads your page in a real headless browser at mobile (375px), tablet (768px) and desktop (1280px) widths and checks each one for: horizontal scrolling, elements wider than the viewport (fixed-width containers, wide tables, oversized images), a viewport meta tag, and how many CSS media queries the page uses. You get a 0–100 responsive score with a clear grade and a prioritised list of fixes.

On phones, horizontal scrolling is the most common — and most jarring — sign of a broken responsive layout. It’s almost always caused by one element that’s too wide: a fixed-pixel container, an un-wrapped table, or an image without max-width. The tool names the widest offending elements so you can find and fix the culprit fast.

Critical. Without <meta name="viewport" content="width=device-width, initial-scale=1">, mobile browsers assume a desktop-width page and shrink it to fit — so even a perfectly responsive CSS layout looks tiny and unusable. It’s the single biggest responsive issue and the first thing to fix.

It renders in a real headless Chromium browser at common device widths, which catches the vast majority of layout and overflow issues quickly. It’s not a full device-lab test across every phone model and OS, but it’s an excellent, instant first pass before you ship.