Mobile Viewport Checker

To check whether a page is set up for phones, paste its URL into the free Mobile Viewport Checker above. It reads the viewport meta tag and flags a missing tag, a fixed width or blocked zooming. Then it loads the page twice, once as a phone and once as a desktop browser, and compares the two versions. Google indexes the mobile version, so the checker flags any title, canonical, robots tag, heading, text or structured data that is missing on mobile. You can check up to 10 URLs at once.

Last updated: 6 November 2026. Written by Saad Raza.

Key takeaways

• Every page needs <meta name="viewport" content="width=device-width, initial-scale=1">. Without it, phones render the page at about 980 px wide and shrink it.
• user-scalable=no or a maximum-scale below 2 stops people zooming, which fails accessibility guidelines. Remove it.
• With mobile-first indexing, Google uses the mobile HTML for ranking. Content, links and schema that exist only on desktop are not counted.
• A responsive design on one URL avoids almost every mobile parity problem. Separate m-dot sites and dynamic serving need extra care.

What the viewport tag does

The viewport meta tag tells a mobile browser how wide to lay out the page. With width=device-width, a phone that is 390 CSS pixels wide lays the page out at 390 pixels, so a responsive design’s mobile styles apply. Without the tag, the browser assumes a desktop-sized layout and zooms out to fit it on screen, leaving tiny text that people have to pinch to read. My guide to the viewport meta tag and SEO covers the history and each setting in detail.

The tag is one line, but it is the foundation of mobile SEO. Google retired its separate mobile-friendly test, so checks like this one, Lighthouse and Chrome’s device mode are now the way to confirm the basics.

Why mobile and desktop HTML must match

Since mobile-first indexing, Googlebot crawls as a smartphone. If your server sends phones a lighter page, with a shorter article, fewer internal links, a different title or no structured data, Google only sees that lighter version. A responsive site sends the same HTML to everyone, so it passes automatically. Sites that use dynamic serving (different HTML on the same URL) or separate mobile URLs such as m.example.com are where problems hide, because nobody looks at the mobile source.

How to use the Mobile Viewport Checker

1. Paste one URL, or up to 10 with one per line.
2. Run the check. Each URL is requested as a phone and as a desktop browser, so each one counts as two checks.
3. Read the summary: the viewport value, whether zooming is allowed, and whether mobile and desktop match.
4. Open each URL’s section for the viewport findings and the mobile-versus-desktop comparison.
5. To test a template before it goes live, paste the HTML (or just the viewport tag) into the second box instead.

What the checker tests

A worked example with real sites

I checked GitHub, BBC News and MDN Web Docs on 6 November 2026. All three passed.

• github.com uses width=device-width with no initial-scale, which the checker notes as information only. Its phone and desktop HTML had the same title, H1, text and links.
• BBC News uses width=device-width, initial-scale=1, the recommended pair, and served identical HTML to both.
• MDN uses initial-scale=1.0, which is the same as 1, and also matched.

Here is what a failing page looks like. A shop page that sends phones width=480, user-scalable=no gets three findings: a fixed width that will not fit most screens, no initial-scale, and blocked zooming. If its mobile title is also shorter (“Shoes” instead of “Red shoes”), the comparison flags that the title differs on mobile, and notes that the server sends different HTML without a Vary: User-Agent header.

How to fix what it finds

• Missing or fixed-width viewport: put <meta name="viewport" content="width=device-width, initial-scale=1"> in the head of every template, then make sure your CSS is responsive. In WordPress this belongs in the theme’s header file.
• Zoom blocked: delete user-scalable=no and any maximum-scale. If a form zooms in on iPhone when tapped, fix it by setting inputs to at least 16 px font size, not by blocking zoom.
• Mobile missing content or links: show the same content on all devices. Collapsing text into tabs or accordions is fine; removing it from the HTML is not. Check your menus too, because links that only exist in a desktop mega-menu are invisible to a smartphone crawler.
• Schema missing on mobile: output the same JSON-LD in both versions, then confirm it with the JSON-LD validator.
• Different canonical or robots on mobile: fix urgently, and confirm with the canonical and noindex checker.

Viewport issues often travel with speed problems on phones. Once the basics pass, work through Core Web Vitals for mobile and test the server response with the TTFB and compression checker, which can also request pages as a phone.

Limits

The checker compares HTML. It does not run JavaScript or apply CSS, so it cannot see text that is too small, buttons that are too close together, or content wider than the screen. Use Chrome DevTools device mode or Lighthouse for layout. Pages that build their content with JavaScript may look nearly empty here on both versions; my explanation of why checkers miss JavaScript content applies. Some pages change slightly on every request (rotating stories, counters), so a small difference in word or link counts is not always a problem. The phone request uses a modern Android Chrome user agent; sites that detect devices another way may respond differently.

Questions about the Mobile Viewport Checker

If your site needs a mobile and technical review, my technical SEO services cover mobile-first indexing, speed and rendering, and you can ask for a free audit. You can also browse the other free technical SEO tools.