✓ Free to Use • No Signup • Live Check — We Fetch the URL for You
Enter a URL and this tool checks the mobile signals that live in the page itself: whether the viewport tag exists and is set correctly (width=device-width), whether an initial scale is declared, how many of the page’s images are responsive (srcset or sizes), and — from Google’s own Lighthouse — the mobile Performance score.
Google indexes and ranks the mobile version of your page first — mobile-first indexing means the phone rendering is not the alternative view, it is the canonical one. A page that squeezes a desktop layout onto a small screen is not merely ugly; it is the version of record, with all its problems attached.
This test is honest about its layer: it checks the signals encoded in the HTML — the viewport declaration that tells the browser how to scale, the responsive-image markup that serves right-sized files — plus Google’s mobile Performance score for the loading experience. It does not render the page on a real device, so tap-target spacing and actual font sizes are outside its scope; open the page on your phone for those.
Google now indexes and ranks the mobile version of your pages by default. This approach, called mobile-first indexing, means the small-screen document is the one that counts: if content, links or structured data exist only in the desktop version, they may as well not exist at all. For most websites, the majority of visitors also arrive on phones, so the mobile experience is not a secondary concern or a nice extra. It is the primary product your audience uses and the primary version the search engine evaluates.
This check looks at the signals that can be verified directly from the page's HTML and from Google's own performance data. It confirms whether a viewport meta tag is present and set correctly, whether the initial scale is defined, and whether images use responsive techniques such as srcset and sizes. It also pulls the mobile Performance score from Google's PageSpeed Insights API for the same URL. Together these results give you a fast, honest first pass before you spend time on deeper device testing.
The most common failure is still the missing viewport tag: without it, mobile browsers assume a wide desktop layout and shrink the whole page until text is unreadable. Close behind are fixed pixel widths that force horizontal scrolling, and viewport settings that disable zoom, which shut out visitors who need to enlarge text. Another frequent problem is declaring the viewport correctly but loading images at full desktop size, leaving the smallest screens to download the heaviest files on the page and draining both data and patience.
Each result in this check maps to a concrete fix rather than a vague warning. A missing or incorrect viewport line points you straight to the template or theme file that generates the page head. Absent srcset attributes identify the image pipeline that needs a responsive variant. A weak Performance score sends you to the heaviest resources first. Be aware of the limit, though: this test reads code and lab data, not a physical phone, so tap-target spacing and real font rendering still need a manual look.
Privacy: to run this check, our server fetches the public URL you enter — the same request any browser or crawler makes. The URL and its results are not stored; close the tab and they are gone.
It is the meta tag that tells a phone browser how wide the page is and how to scale it: width=device-width, initial-scale=1 is the standard form. Without it, phones render the page as if it were roughly 980 pixels wide and shrink it — the classic unreadable desktop-on-phone result.
Because responsive frameworks still ship broken pages: a template that forgets the viewport on one layout, a fixed-width embed that bursts the layout, images without srcset sending desktop files to phones. The test checks the page you point it at, not the design system’s intentions.
The same thresholds as any speed work: the green zone is 90+, with LCP under 2.5 seconds on the throttled mobile test. The full metric set is in the <a href="/seo-tools/website-speed-test/">Website Speed Test</a>.
No — and it says so on the page. It covers the machine-checkable signals quickly and repeatably; a thirty-second look at the real page on your own phone still catches the layout problems no HTML check can see.
Tools handle the technical setup. Rankings come from authority — browse 1,502 real publisher sites with live metrics and fixed prices, or see our packages.