Paste HTML or drop a file and see it at real phone, tablet and desktop widths at the same time.
How It Works
Drop the page into the source editor or open an .html file from your computer. The sample is a small landing section whose nav and grid change shape between phone and desktop widths.
Switch between Phones, Tablets, Desktops and All, turn phones and tablets to landscape with Rotate, or add a custom width from Options. Each frame renders at the exact pixel width shown in its header.
Edit the source and every frame updates as you type. When it looks right everywhere, publish it to a live link. No account is needed for the 30-minute link, and claiming it is free.
About This Tool
It renders one HTML file at several real device widths at the same time, so you can see where the layout breaks without resizing a browser window over and over.
A page that looks fine on your laptop can fall apart at 375 pixels: a navigation bar that wraps onto three lines, a two-column grid that squeezes instead of stacking, a headline that runs off the right edge. This responsive design checker shows the same HTML in a row of frames, each at the CSS width of a real device, so the phone, tablet and desktop versions sit side by side and the differences are obvious at a glance. Change the source and every frame re-renders together.
Anyone holding an HTML file they did not build from scratch. If ChatGPT or Claude wrote you a landing page, a designer handed over a template, or a course gave you a starter file, you probably checked it once on your own screen and moved on. A mobile friendly test is the step that catches what that screen hid. It is equally useful for a quick website responsive test before sending a page to a client, or for teaching yourself what a media query actually changes: edit the breakpoint in the source and watch the frames react.
Each frame is a sandboxed iframe laid out at the exact width of the device named in its header, using the CSS pixel widths those devices report to media queries: iPhone SE at 375, iPhone 15 at 393, Pixel 8 at 412, iPad Mini at 768, iPad Pro at 1024, then 1280 and 1440 for laptops and desktops. Frames wider than 768 pixels are rendered at their true width and scaled down to fit the strip; the page inside still sees its full width, so a min-width: 1024px rule behaves the way it would on a real laptop. Rotate turns phones and tablets to landscape using each device's real long side, and Options adds a frame at any width you type. Everything runs in your browser: the HTML is never sent anywhere while you test.
This is a width tester, not a device emulator. It does not pretend to be a phone's browser, spoof a user agent, simulate touch, or apply a device pixel ratio, and it cannot load a live URL, because almost every site forbids being embedded in another page. If your page depends on any of that, a real device or the emulator built into your browser's developer tools is the right next check. For a single, larger preview, the HTML viewer is better; to find the unclosed tag behind a layout bug, run the file through the HTML tester first.
The frames tell you the layout works; a live link lets you confirm it on a real phone in your hand. The publish button below puts the source on a free OxyPages subdomain with HTTPS, in seconds, with no account. The link lasts 30 minutes; claiming it is free and keeps it permanently, with your own address and, on paid plans, a custom domain. Instant publishing accepts pages up to 5 MB. Read how it works or compare plans.
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The whole pitch fits in one sentence: your HTML, on a link, in seconds.
Drag and drop your HTML file(s), folders, or ZIP file
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No account needed. Your unclaimed website stays live for 30 minutes on a free subdomain. Claim it to your account to keep it permanently.
