Responsive Website Tester
Preview a website on multiple screen sizes at once.
Responsive Website Tester
See how a website looks on phones, tablets and desktops at the same time. Enter a URL, pick devices such as iPhone 15, Pixel 8, iPad mini or a 1920×1080 desktop, and the page loads in side-by-side frames that use each device's real CSS viewport width, scaled down to fit your screen.
Why test responsive design?
More than half of web traffic comes from mobile devices, and Google indexes the mobile version of your pages first. A layout that looks perfect on a laptop can overflow, hide buttons or shrink text to an unreadable size on a 360-pixel-wide phone. Seeing several breakpoints next to each other makes it easy to spot horizontal scrolling, overlapping elements, oversized images and navigation that does not collapse.
Features
- 8 device presets covering small and large phones, tablets, laptops and full-HD desktops.
- Custom size for any breakpoint you use in your CSS, for example 600 or 1024 pixels.
- Landscape mode rotates every device at once.
- Accurate media queries: each frame keeps the true viewport width and is scaled with CSS transforms, so
@media (max-width: 768px)rules fire exactly as on the device. - Works with localhost and staging URLs because pages load directly in your browser.
Tips for better mobile layouts
Make sure every page has a <meta name="viewport" content="width=device-width, initial-scale=1"> tag, use relative units and flexible grids, keep tap targets at least 44 pixels tall, and serve responsive images with srcset. If a frame stays empty, the site blocks embedding — open it directly with your browser's developer tools device mode. Checking a server's reachability instead? Try the Open Port Checker.
Frequently Asked Questions
Why is a device frame blank?
The website forbids being shown inside other pages with an X-Frame-Options header or a Content-Security-Policy frame-ancestors rule. Large sites such as Google, Facebook and banks do this. Use the Open button or your browser's device toolbar instead.
Does this emulate the real device?
It reproduces the viewport size, so CSS media queries and layouts behave as on the device. It does not change the user agent, touch events or pixel density, so server-side mobile detection and hover effects may still differ.
Can I test a site on localhost?
Yes. The frames load directly in your browser, so http://localhost:3000 works while your development server is running — nothing is proxied through our server.