Multi-Device Tester

A multi-device tester lets you preview how a website looks across different screen sizes — desktop, tablet, and mobile — simultaneously. It helps developers and designers quickly spot responsive design issues without needing physical devices. By entering a URL, you can see real-time rendering in three viewports, making cross-device testing fast and efficient.

Many websites set the X-Frame-Options or Content-Security-Policy HTTP headers to prevent being embedded in iframes. This is a security measure against clickjacking attacks. Sites like Google, Facebook, YouTube, and many others block iframe embedding. If your preview is blank, try a different URL or use the "Open in new tab" button to view the site directly.

We use three common viewport sizes: Desktop at 1920×1080 (standard full-HD monitor), Tablet at 768×1024 (iPad portrait dimensions), and Mobile at 375×667 (iPhone SE/6/7/8 size). These represent widely used breakpoints. You can rotate tablet and mobile views to simulate landscape orientation for additional testing coverage.

The preview accurately reflects how your site renders at specific viewport widths. However, it uses your browser's rendering engine, so it won't emulate device-specific behaviors like touch events, iOS Safari quirks, or Android Chrome differences. For full accuracy, test on actual devices or use browser DevTools device emulation, which can simulate touch, user agents, and sensor APIs.

Common responsive breakpoints include: 320px (small phones), 375px (iPhone), 414px (iPhone Plus), 768px (iPad), 1024px (iPad Pro / small laptops), 1280px (standard laptops), and 1440px+ (desktops). We recommend testing at least mobile (375px), tablet (768px), and desktop (1280px+) to cover the majority of users. Use CSS media queries to adapt your layout at these thresholds.

No, this is a client-side preview tool that renders websites using your browser's default user agent. It shows how the layout responds to different viewport widths but does not spoof device-specific user agents. For user agent emulation, use Chrome DevTools (F12 → Network conditions → User agent) or Firefox Responsive Design Mode.

You can enter http://localhost:PORT or http://127.0.0.1:PORT in the URL field to test locally running sites. Make sure your local server is running and accessible. Note that if your local server sets X-Frame-Options headers, the preview may be blocked. You can temporarily disable those headers in your dev server configuration for testing purposes.

X-Frame-Options is an HTTP response header that controls whether a page can be displayed inside an iframe. Values include DENY (no embedding allowed), SAMEORIGIN (only same-domain embedding), and ALLOW-FROM uri. The newer Content-Security-Policy frame-ancestors directive serves a similar purpose. These security headers prevent clickjacking but also block legitimate preview tools like this one.