What Is Responsive Breakpoint Previewer?
Responsive Breakpoint Previewer shows how any URL renders at different screen sizes — from mobile phones to ultrawide monitors. Preview your site at standard device widths, custom breakpoints, or popular device dimensions to catch layout issues before they reach production.
How to Use This Tool
Enter a URL and select from preset device sizes (iPhone, iPad, laptop, desktop) or set custom width and height values. The tool renders the page in an iframe at each breakpoint so you can compare layouts side by side. Toggle between portrait and landscape orientations. Everything runs in your browser — the URL loads directly in the preview frame.
Why Use Responsive Breakpoint Previewer?
Chrome DevTools responsive mode only shows one size at a time. This tool lets you view multiple breakpoints simultaneously, making it faster to spot layout breaks, text overflow, and alignment issues across the full range of screen sizes. It’s free, instant, and requires no browser extensions. For a detailed walkthrough, see our step-by-step guide.
Common Use Cases
Sanity-checking a layout at the breakpoints your stylesheet actually targets, instead of guessing what 768px or 1024px will look like by dragging a window. Reviewing a client's draft in front of them with multiple viewport widths visible side-by-side. Catching the typical mid-breakpoint failure modes — a heading that breaks awkwardly at 900px, a navigation that collapses too early on tablets, an image that loses focal-point cropping at landscape phone widths.
Comparing how a page handles iPad portrait vs landscape vs a Pixel 7 vs a wider-than-laptop external monitor in one screen, instead of resizing four times. Spotting regressions after a CSS change: open the previewer, change the file, watch all four widths reflow at once. The tool is also useful for content reviews, where non-designers can see at a glance which breakpoints a piece of copy survives and which break it.
How We Compare
Chrome DevTools device mode is the gold standard for one-viewport inspection and ships with realistic device presets, touch emulation, and throttling. The limitation is that it shows one device at a time, so cross-breakpoint comparison means tabbing between presets. Polypane and Sizzy are paid multi-viewport browsers that solve exactly that problem and add scroll/click sync, but they're desktop apps with subscription pricing.
This tool sits between them: open it in any browser, paste any URL, see four common breakpoints rendered simultaneously, no install, no account. Pair it with our container query builder when you're converting component-level responsive rules off the media-query layer.
A practical pointer: the previewer iframes the target URL, so sites that block iframe embedding via X-Frame-Options or Content-Security-Policy: frame-ancestors won't render. That's the site's security setting, not a tool bug — testing those sites needs a local dev environment or browser DevTools instead.
Frequently Asked Questions
Built by Derek Giordano · Part of Ultimate Design Tools