Mobile-first indexing

What it is

“Google uses the mobile version of a site’s content, crawled with the smartphone agent, for indexing and ranking. This is called mobile-first indexing.” A mobile version isn’t required to be included in results, but Google very strongly recommends one.

Officially documented · Google Search Central

Responsive design avoids the problem

Of the three configurations (responsive design, dynamic serving, separate URLs), “Google recommends Responsive Web Design because it’s the easiest design pattern to implement and maintain.” The rest of Google’s guidance applies only to dynamic serving and separate URLs. With responsive design, the content and metadata are the same on both.

Officially documented · Google Search Central

If mobile and desktop differ

“Make sure that your mobile site contains the same content as your desktop site.” Moving content into accordions or tabs on mobile is fine. If the mobile page deliberately has less content, expect some traffic loss, because Google indexes the site from its mobile version.

Officially documented · Google Search Central

“Use the same robots meta tags on the mobile and desktop site.” A different tag on mobile, especially noindex or nofollow, can stop Google from crawling and indexing the page. Google also won’t load content that needs a user interaction, such as swiping, clicking or typing, to appear.

Officially documented · Google Search Central

Also keep these equivalent across both versions:

• headings;
• structured data, with URLs pointing at the mobile URLs;
• the title element and meta description;
• image alt text, and ideally the same image URLs, to avoid a temporary image traffic loss.

Separate mobile URLs (m-dot)

Serve the same error status on both sites. If the mobile version of a page is an error page, “this page will be missing from the index.” Avoid URL fragments (#) in mobile URLs, because they are usually not indexable.

Officially documented · Google Search Central

For AI search

To appear as a link in Google’s AI features, a page must be indexed and eligible to show with a snippet (Google AI Overviews). Indexing uses the mobile version, so content missing on mobile is missing there too. Other AI crawlers fetch pages with their own user-agents and may receive the desktop version. Responsive design keeps every crawler on the same HTML.