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Mobile-First Indexing: What It Is and How to Check Your Site

Google indexes the mobile version of your pages. Here is what that means, the content and markup that must match, and how to test your site for free.

By freeseobot Editorial · Published · 5 min read

Google indexes and ranks your site using the mobile version of your pages. According to Google Search Central, mobile-first indexing means Google uses the mobile version of a site's content, crawled with the smartphone agent, for indexing and ranking. If something is on your desktop page but missing from your mobile page, Google may never see it.

This guide explains what has to match between the two versions, which mistakes cause problems, and how to check your own site.

What is mobile-first indexing?

Mobile-first indexing is Google's practice of crawling and storing your pages as a phone would see them. It decides which version of your page is the one Google reads.

Google also says a mobile version is not required to appear in Search, but is "very strongly recommended."

Which mobile setup does my site use?

Google's documentation describes three configurations:

  • Responsive design. One URL and the same HTML for every device. Google calls it "the easiest design pattern to implement and maintain."
  • Dynamic serving. One URL, but different HTML depending on the device, using user-agent detection and the Vary header.
  • Separate URLs. Different HTML on different addresses, such as an m-dot subdomain.

If your site is responsive, which covers most modern themes and site builders, the two versions are the same page and most of the problems below cannot happen. Google's best-practice guide is aimed at dynamic serving and separate URL sites.

What must match between mobile and desktop?

Google lists these items. Check each one if your mobile page is different from your desktop page.

Content. The mobile page should carry the same primary content as the desktop page. Google suggests using accordions or tabs to save space instead of removing content. Keep headings consistent.

Robots rules. Use the same robots meta tags on both versions. A noindex or nofollow that appears only on mobile can cause the page to drop out. Do not block resources with robots.txt Disallow.

Titles and descriptions. Keep the title element and meta description equivalent on both versions. Our guide to title tags and meta descriptions covers how to write them.

Structured data. Mobile pages should carry the same markup as desktop. Google names Breadcrumb, Product and VideoObject as the ones to prioritise. If you use separate URLs, the URLs inside the markup should point to the mobile pages.

Images. Use high-quality images in supported formats with stable URLs, and keep the same alt text, titles, captions and file names as on desktop. Google warns that changing image URLs can cause a temporary loss of image traffic. See image SEO for the basics.

Videos. Use stable URLs, supported tags (<video>, <embed>, <object>), matching video structured data, and place the video where a phone visitor can find it.

Lazy loading. Primary content should not need a swipe, click or typing to appear.

What extra rules apply to separate mobile URLs?

If you run an m-dot site, Google adds these:

  • Serve the same error status code on both versions.
  • Do not use URL fragments on mobile pages.
  • Do not redirect many desktop pages to a single mobile target, such as the mobile home page.
  • Verify both versions in Search Console.
  • Link hreflang mobile-to-mobile and desktop-to-desktop.
  • Make sure your server can handle a possible rise in crawl rate.
  • Use consistent robots.txt rules for both versions.
  • Treat the desktop page as the canonical. The mobile page points to it with rel="canonical", and the desktop page points to the mobile page with rel="alternate" and a media query.

Maintaining two sites is more work and more room for error. If you can move to a responsive design, you remove this whole list.

Which mistakes cause ranking drops?

Google's troubleshooting section lists the common causes. Examples from that list:

  1. A noindex on the mobile version only.
  2. Mobile pages that return an error page.
  3. Missing or blocked images, or missing alt text.
  4. Missing titles or meta descriptions on mobile.
  5. Structured data present on desktop but absent on mobile.
  6. Resources blocked by robots.txt, so the page renders incorrectly.

For the first and last items, read noindex vs robots.txt to see how the two rules interact.

How do I check my site for free?

  1. Look at the real mobile page. Open your site on a phone, or use the device mode in your browser's developer tools. Compare the headings, text, images and links with the desktop page.
  2. Use URL Inspection. In Search Console, inspect a URL and view the HTML Googlebot received. Confirm your main text, title and structured data are in it.
  3. Run an audit. The freeseobot SEO checker crawls your pages and reports missing titles, descriptions, alt text, structured data, viewport settings and noindex pages. It also checks that pages are set up for phones.
  4. Check page experience. Slow phones are a separate problem from indexing. Our Core Web Vitals guide covers LCP, INP and CLS.

Does a hidden accordion or tab hurt me?

Google's mobile-first guidance recommends accordions and tabs as a way to save space, so they are not a problem in themselves. The advice is to avoid removing content from the mobile version. The page we read does not give separate guidance on hidden content beyond this, so we make no further claim about it.

Questions

Do I need a separate mobile site?

No. Google recommends responsive design as the easiest to maintain. A separate mobile site is allowed but adds duplicate-management work.

Is my desktop-only site excluded from Google?

No. Google says a mobile version is not required for inclusion in Search results. It is very strongly recommended, though.

Does mobile-first indexing change my rankings by itself?

Google's guide describes what to fix so that mobile-first indexing does not cause drops. It does not describe a ranking boost or penalty for the switch itself.

Do desktop visitors see the mobile page?

No. It affects what Google stores and ranks. Visitors on desktop still get your desktop layout.

How often should I check?

After every theme change, plugin update or redesign. Our 30-minute weekly routine includes a quick audit that catches most regressions.

Sources

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