Mobile Friendly Checker: Test Any Page at Real Phone Widths

10 min read

There is no official mobile friendly checker any more. Google retired its Mobile-Friendly Test in December 2023, and the tool it told everyone to use instead has since dropped the mobile checks as well. The checker below fills that gap the honest way: it renders your page at real phone and tablet viewport widths, inside your own browser, so you can see what somebody on a small screen actually gets.

How to read what the mobile friendly checker shows you

The widths above are not invented. They are the viewport sizes Chrome DevTools ships as device presets, taken from Chromium’s own emulation configuration, so what you see here matches what you would see doing it by hand in DevTools.

Start with the narrowest frame. The Galaxy Z Fold 5 preset is 344 CSS pixels wide folded, which makes it the strictest realistic test on the list. A layout that holds together at 344px will hold together on almost any phone in use.

The mobile friendly checker above deliberately does not grade any of this for you. It shows you the page and leaves the judgement where it now belongs. Look for four specific failures, in this order:

• Content cut off at the right edge. Something on the page has a fixed width wider than the screen. This is the single most common mobile defect and the easiest to miss on a desktop monitor.
• Text you would have to zoom to read. Google no longer treats this as a ranking signal, but a visitor squinting at 9px body copy still leaves.
• Buttons and links packed too tightly. If two tap targets sit within a thumb’s width of each other, people hit the wrong one.
• Navigation that vanishes or breaks. Menus that collapse into a hamburger sometimes collapse into nothing at all below a certain width.

Rotating to landscape is worth a moment too. Plenty of layouts that behave in portrait break when the viewport gets short rather than narrow, and sticky headers are the usual culprit.

Why there is no official verdict left to give you

This part is worth understanding, because most guides on the subject are describing a world that stopped existing three years ago.

On 1 December 2023, Google retired three things at once: the Mobile Usability report inside Search Console, the Mobile-Friendly Test tool, and the Mobile-Friendly Test API. Its reasoning was not that mobile stopped mattering. Google said the opposite — that mobile usability “remains critical” — but argued that better resources had appeared since the tools launched, and named Lighthouse in Chrome as one of them.

So for about two years the honest advice was: use Lighthouse, check the SEO section, it flags the same things the old tool did.

That advice expired on 10 October 2025, when Lighthouse 13 shipped. It removed the font-size audit outright, with a blunt explanation in the release notes: “While small fonts is a legibility issue, there are no signals that this remains an SEO concern today.” The separate viewport audit was retired and replaced by a new viewport-insight audit, which now sits under Performance rather than Best Practices.

Read Lighthouse’s current default configuration and the SEO category comes back as eleven audits: crawlability, document title, meta description, HTTP status code, link text, crawlable anchors, robots.txt, image alt text, hreflang, canonical and structured data. Not one of them is a mobile-usability check. The tap-targets audit, which used to flag buttons sitting too close together, is not in that configuration either.

There is still a meta-viewport audit, but it lives in the Accessibility category and it is testing something narrower than the old tool did — whether your viewport tag blocks pinch-zoom, which is an accessibility problem rather than a layout one.

The net result: Google retired its mobile-friendliness verdict, pointed at Lighthouse, and Lighthouse subsequently dropped the mobile-usability audits too. Anyone telling you to run a page through Google’s checker, or to read the mobile flags in Lighthouse’s SEO report, is describing tooling that no longer works that way. That is the gap a mobile friendly checker built around viewport previews is there to fill.

What still actually matters

Losing the badge does not mean mobile rendering stopped counting. It means the things that count are now measured somewhere else, or not measured for you at all.

Mobile-first indexing has not changed

Google indexes the mobile version of your pages. If something is missing, broken or unreachable at phone width, that is the version Google forms its opinion from — not the desktop layout you built it on. This is the reason a rendering problem is an SEO problem even with no mobile-friendly score attached to it.

Core Web Vitals are still scored

Performance did not get quietly dropped the way the usability audits did. Largest Contentful Paint, Cumulative Layout Shift and Interaction to Next Paint are all still measured, still reported separately for mobile, and still available in Search Console. That is what the PageSpeed Insights button in the tool above gets you: Google running Lighthouse against your URL on its own hardware, with the mobile form factor selected.

Layout and tap targets are now your own judgement call

Nothing automated will tell you your buttons are too close together any more. That does not make it a non-issue; it makes it an issue you have to see for yourself, which is precisely what looking at the page at 344 and 375 pixels is for. Running a page through a mobile friendly checker at several widths takes under a minute and catches the breakages no report will flag for you now.

Testing a site that is not live yet

A mobile friendly checker that runs in your browser can only reach pages that are on the public internet. If your site is still running on localhost, no online tool can see it, and neither can your phone — “localhost” literally means “this machine”.

The fix is to use your computer’s local network IP address instead, with the phone on the same Wi-Fi, and to make sure your dev server is listening on the network rather than only on the loopback interface. Our guide to testing your website on mobile devices walks through that properly, along with the other free tools worth knowing about.

Mobile Friendly Checker FAQ

Why does Google’s Mobile-Friendly Test no longer work?

It was retired on 1 December 2023, together with the Mobile Usability report in Search Console and the Mobile-Friendly Test API. Google did not replace it with an equivalent one-click tool; it pointed users towards Lighthouse in Chrome instead.

Is there still a pass or fail mobile-friendly result anywhere?

Not from Google. Bing still runs a public mobile friendliness test that returns a verdict without a sign-in, and the tool above links straight to it for whatever URL you entered. Treat a pass as useful; Bing’s tool reports trouble on perfectly valid URLs often enough that a failure is worth confirming elsewhere before you rewrite anything.

Why is the preview blank for some websites?

Because those sites send a header — X-Frame-Options, or a frame-ancestors directive in their Content Security Policy — instructing browsers not to render them inside another page. It is a defence against clickjacking, it is working as intended, and it affects every preview tool of this kind equally. It has no bearing on how the page ranks or how it looks on a real handset.

Does this mobile friendly checker send my URL anywhere?

No. The preview is built from iframes in your own browser, so the request to your site comes from your machine, the same as typing the address into a tab. Nothing is logged here and nothing is stored. The PageSpeed Insights and Bing buttons do hand the URL to Google and Microsoft respectively, but only when you click them.

Is a responsive site automatically mobile friendly?

Usually, but not always. Responsive means the layout adapts to the viewport. Mobile friendly is the broader question of whether the result is usable — readable text, reachable buttons, a page that loads before somebody gives up on a patchy connection. A responsive theme can still ship a 600px-wide table that nothing can reflow, which is the sort of thing a mobile friendly checker surfaces in seconds and a desktop monitor hides completely.

Do I still need to test on a physical phone?

For the final check, yes. A viewport preview shows layout accurately, but it cannot reproduce a real thumb on real glass, an older phone’s processor, or the specific quirks of iOS Safari. Use the preview to catch the obvious breakages quickly, then confirm on a handset before you ship something important.

Sources

• What’s new in Lighthouse 13 — Chrome for Developers, for the removed audits and Google’s stated reasoning.
• Mobile-first indexing — Google Search Central documentation.
• Lighthouse’s current SEO category audit list, read from the default configuration in the Lighthouse repository.