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Mobile Responsive Checker

This mobile responsive checker loads any web page inside real device viewports so you can see how it looks on phones, tablets and laptops without owning them. Paste a URL and press Preview. The multi-device canvas shows several devices side by side, drawn from 12 presets that include iPhone, Pixel, Galaxy and iPad sizes plus three laptop and desktop screens, and you can add your own sizes or turn every phone and tablet to landscape. The single device view adds custom width and height and quick breakpoint buttons for 320 to 1440 pixels. Many sites refuse to load inside frames, so Device UA mode fetches the page through our server with each device's user agent. A share link reopens the same URL, devices and sizes for a teammate.

Always freeNo sign upRuns in your browser
Presets
Phones
Tablets
Desktop
Custom
70%4 devices · full-width auto-fit
Enter a URL and press Preview to render it across 4 devices at once. They fill the full width of your screen.

How to use

01

Enter the URL and press Preview

Type or paste the page address, such as example.com. It loads in every selected device at once. If frames stay blank, switch from Direct to Device UA and it reloads through our server.

02

Pick devices or a custom size

In the canvas, choose a preset, toggle devices, add a custom size or tick Landscape, and use the Size slider to zoom. In Single device, pick one device, rotate it, or enter a custom size.

03

Check the layout at each width

Scroll inside each frame to check menus, images and tables. Press Reload all after a fix, open the page in a real window of that size, or copy the share link for your team.

Why Mobile Responsive Checker

Device viewports in the checker

Each preset uses the device's real CSS viewport, the size a responsive layout responds to, and its device pixel ratio. Device UA mode also sends that device's real browser user agent. CSS media queries react to these CSS pixel widths, not to the physical resolution, which is why a phone with a 1179-pixel-wide screen still gets your 393-pixel mobile layout.

DeviceViewport (CSS px)Pixel ratio
iPhone SE375 x 6672
iPhone 15 / 16393 x 8523
iPhone 15 Pro Max430 x 9323
Pixel 8412 x 9152.625
Galaxy S23360 x 7803
iPad mini768 x 10242
iPad Air820 x 11802
iPad Pro 11-inch834 x 11942
iPad Pro 13-inch1024 x 13662
Laptop1366 x 7681
MacBook 14-inch1512 x 9822
Desktop HD1920 x 10801

Why frames stay blank, and how Device UA mode fixes it

In Direct mode your browser loads the site straight into each frame. Many sites send X-Frame-Options: DENY or SAMEORIGIN, or a Content-Security-Policy with frame-ancestors, to stop other pages from embedding them. It protects against clickjacking, and the browser obeys it by leaving the frame blank.

Device UA mode takes a different route. Our server requests the page with the chosen device's user agent, removes frame-blocking meta tags, adds a base address so images and styles still load from the original site, and serves the result from our own domain. The frame then shows the HTML the site sends to that device, including any mobile-specific version.

The trade-off is that the page runs in a sandbox. Scripts work, but cookies, logins and some single-page apps may not behave as they do on a phone. Use Direct mode when it works, and Device UA mode when it does not.

Common questions

How is this mobile responsive checker different from resizing my browser?
It shows several exact device widths at the same time, so you can compare a phone and a tablet side by side instead of dragging one window. Device UA mode also sends each device's user agent, so sites that serve different HTML to phones show their mobile version.
Which device sizes does the responsive checker include?
There are 12 presets: five phones (iPhone SE, iPhone 15, iPhone 15 Pro Max, Pixel 8 and Galaxy S23), four iPads, and three laptop or desktop screens up to 1920 pixels wide. The single device view also takes any custom width and height.
Can I test a custom screen width in the responsive checker?
Yes, in both views. In Single device, use a breakpoint button (320, 375, 768, 1024 or 1440) or type a width and height and press Apply size. In the canvas, type a size and press Add size to show it next to the presets. Widths from 240 to 2560 pixels and heights from 240 to 1600 pixels are accepted.
Can I run a mobile friendly test on a site that blocks iframes?
Usually, yes. Switch to Device UA mode and our server fetches the page with the device's user agent, then shows it from our own domain, so the site's frame blocking no longer applies. Scripts run with limits in this mode, so pages that depend on cookies or logins may not work fully.
Why do some frames stay blank in Direct mode?
The site sends an X-Frame-Options header or a Content-Security-Policy frame-ancestors rule that tells browsers not to show it inside another page. Your browser obeys, so the frame stays empty. Device UA mode gets around it.
Does the responsive design tester show landscape orientation?
Yes. In Single device, pick a phone or tablet and press Landscape to swap width and height. In the canvas, tick Landscape to turn every phone and tablet at once. Laptop and desktop frames stay in their normal orientation.
Can I share a responsive preview with my team?
Yes. After you press Preview, Copy share link gives you an address that reopens the same URL, view, mode, devices, custom sizes and orientation. Anyone who opens it sees the same set of frames, loaded live from the site at that moment.
Is checking a site on emulated device sizes as accurate as real hardware?
It is accurate for layout: widths, breakpoints and how content reflows. It still uses your own browser's engine, so Safari-only quirks, touch behavior, fonts and performance on a real phone can differ. Check important pages on at least one real device before launch.
What does the @2x or @3x label under each device frame mean?
It is the device pixel ratio: how many physical pixels the screen uses for each CSS pixel. The preview lays the page out in CSS pixels, which is what matters for responsive design. It does not reproduce the sharpness of a high-density screen.
Can the mobile responsive checker test a page behind a login or on localhost?
Not reliably. Device UA mode fetches the page from our server, which has no access to your login or your own computer. Direct mode loads it in your browser, but many browsers block cookies inside frames and block plain http pages inside an https site, so put staging on a public URL.

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