Developer

Responsive screen tester

Preview any URL in an iframe at mobile, tablet, laptop, and desktop widths without leaving the page.

Device presets

Mobile

Tablet

Laptop

Desktop

Ultrawide

If the preview appears blank, the site may have blocked embedding. Test on sites you control for best results.

100% private. All processing happens locally in your browser — no files or data are ever sent to a server.

How to use Responsive screen tester

01 Paste or type your input into the text field provided
02 The output generates instantly as you type
03 Click Copy to send the result straight to your clipboard

Frequently asked questions

Common questions about Responsive screen tester.

Is Responsive screen tester free to use?

Yes, Responsive screen tester is completely free. No account, subscription, or payment is ever required — just open the page and start using it.

Does Responsive screen tester upload my data to a server?

No. Responsive screen tester runs entirely in your web browser using client-side JavaScript. Your files, text, and data never leave your device, making it 100% private.

Can I use Responsive screen tester on my phone or tablet?

Yes. Responsive screen tester is fully responsive and works on all modern smartphones, tablets, and desktop browsers without installing any app.

Does Responsive screen tester work without an internet connection?

Yes. Once the page has loaded, Responsive screen tester works fully offline — all processing is done locally in your browser.

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About Responsive screen tester

The Responsive Screen Tester loads any URL inside a resizable iframe and lets you toggle between preset viewport widths — 320px (mobile S), 375px (mobile M), 768px (tablet), 1024px (laptop), 1440px (desktop), and 2560px (4K). It is a quick way to check responsive breakpoints, test layouts across device categories, and identify overflow or wrapping issues without switching browser windows or using DevTools. Note: some websites set X-Frame-Options or Content-Security-Policy headers that prevent iframe embedding — the tester shows a friendly message in these cases.