Free Responsive Design Tester
See how a web page looks on a phone, tablet and desktop side by side, and get a list of mobile-friendly code problems to fix.
Responsive Design Tester: See how a web page looks on a phone, tablet and desktop side by side, and get a list of mobile-friendly code problems to fix. It is free, needs no sign-up and runs in your browser. How to use it: 1) enter the page address; 2) switch between all sizes, phone, tablet and desktop previews; 3) fix the items flagged in the mobile code checks. The tool does two things. First, our server downloads the page and checks the HTML for common mobile problems.
How the responsive tester works
The tool does two things. First, our server downloads the page and checks the HTML for common mobile problems. Second, if the site allows it, your browser shows the live page in three frames sized like real devices: a phone at 360 pixels wide, a tablet at 768 and a desktop at 1280, scaled down to fit your screen.
Mobile code checks
- Viewport meta tag: without width=device-width, phones show a tiny zoomed-out desktop page.
- Zoom blocking: user-scalable=no hurts people who need to zoom.
- Media queries: we look for width-based CSS rules in the page and its first stylesheets.
- Fixed widths: inline widths over 400 pixels can cause sideways scrolling.
- Tables: wide tables need a scrolling wrapper on small screens.
- Small text: inline font sizes under 12 pixels.
- Tap targets: tiny or crowded links that are hard to tap.
- Responsive images: srcset lets phones download smaller files.
Why some sites cannot be previewed
Many sites send X-Frame-Options or a Content-Security-Policy rule that stops other websites from showing them in a frame. This is a normal security setting, so we explain it and show the code checks only.
Limitations
Previews run in a locked sandbox, so cookie banners, logins and some scripts may behave differently. The code checks are best-effort and read the HTML, not the final rendered layout. Test on a real phone before launch.
Responsive Design Tester FAQs
How do I check if my website is mobile friendly?
Enter your page here to see phone, tablet and desktop previews and a list of mobile code issues. Then open the site on a real phone and check that text is readable without zooming, buttons are easy to tap and nothing scrolls sideways.
Why can’t I see a preview of some websites?
Those sites send a security header, X-Frame-Options or a frame-ancestors rule, that blocks them from being shown inside other websites. This protects against clickjacking. The mobile code checks still work, and you can use your browser’s device mode for a visual check.
What screen sizes should I test?
Test at least a small phone around 360 pixels wide, a tablet around 768 and a laptop around 1280. These cover the most common breakpoints. Also check landscape phone views and very large screens if your audience uses them. Our previews cover the first three sizes.
Does mobile friendliness affect Google rankings?
Yes. Google uses mobile-first indexing, which means it mainly looks at the mobile version of your site for ranking. A layout that breaks on phones, tiny text or a missing viewport tag can hold your pages back and lose visitors.
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