• Google indexes the mobile version of every site. The transition completed in 2023 and 2024.
• Responsive design is the recommended setup because there is only one version to maintain.
• Mobile and desktop need the same content, links, metadata and structured data.
• Content inside accordions and tabs is indexed normally.
• Sites that do not work on mobile at all may not be indexed.

For most of its history Google indexed the desktop version of a page. As mobile searches overtook desktop, that stopped making sense. Google began moving sites to mobile-first indexing in 2016 and finished the job across 2023 and 2024. Today Googlebot Smartphone is the primary crawler for effectively every site, and since July 2024 Google has said that pages which are not accessible on mobile devices will no longer be indexed.

What it actually means

There is still only one index. "Mobile-first" means the mobile rendering of your page is the one Google evaluates. Your desktop site can be magnificent. If the mobile version has less content, fewer links or missing markup, the reduced version is what counts for rankings on every device.

Three ways to serve mobile users

• Responsive design: same URL, same HTML, CSS adapts the layout. This is Google's recommendation and by far the least error-prone.
• Dynamic serving: same URL, different HTML depending on user agent. Requires a Vary: User-Agent header and careful parity checks.
• Separate URLs: an m-dot site. Needs rel=alternate and rel=canonical annotations between versions and is the hardest to maintain. If you still have one, migrating to responsive is usually worth the effort.

Parity checklist

If mobile and desktop differ in any way, check that the mobile version has:

• The same primary content, including text, images and video.
• The same headings.
• The same internal links. Simplified mobile menus often drop important links.
• The same title, meta description, robots directives, canonical and hreflang.
• The same structured data.
• The same image alt text and good quality images with stable URLs.

Hidden content

Content placed in accordions, tabs or "read more" sections for the sake of a small screen is indexed and given full weight, provided it is in the HTML on load. Content fetched only after a tap is not seen.

Usability basics

 <meta name="viewport" content="width=device-width, initial-scale=1" /> 

• Include the viewport meta tag.
• Use readable font sizes without zooming.
• Make tap targets large enough and well spaced.
• Avoid horizontal scrolling.
• Avoid intrusive interstitials that cover content on arrival. Legally required notices such as cookie consent are acceptable.

Google retired the Mobile Usability report and the Mobile-Friendly Test in late 2023. Lighthouse and Chrome DevTools device emulation now fill that gap.

Common mistakes

• Trimming content on mobile "to keep it clean".
• Lazy-loading primary content on mobile that requires interaction.
• Blocking resources for the smartphone crawler.
• Different robots directives on mobile and desktop.
• Desktop-only structured data.
• Mobile ads pushing the main content far down the page.

How to test

• URL Inspection shows which crawler fetched the page and the rendered mobile HTML.
• Crawl with a smartphone user agent and compare against a desktop crawl for word count, links and metadata.
• Chrome DevTools device mode for layout and tap target checks.
• Core Web Vitals filtered to mobile, where scores are almost always worse than on desktop.

The GEO angle

AI crawlers do not have a mobile-first policy. They take whatever HTML the server gives their user agent, typically the desktop or default response. This is another reason responsive design wins: one set of HTML means search engines, AI crawlers and users all get the same content.

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