What is mobile-first indexing?
Mobile-first indexing means Google uses the mobile version of your pages, as seen by its smartphone crawler, to decide what to index and how to rank it. This applies to desktop searches too. If content, links, or structured data exist only on the desktop version, Google may not see them at all.
Google began the shift in 2016, made it the default for new sites in 2019, and finished moving the remaining sites in 2024. It now crawls virtually all sites with its smartphone crawler, and a site that does not work on mobile devices at all may not be indexed.
How it works
Googlebot Smartphone fetches and renders your pages as a phone would. What it finds is what gets indexed. For a responsive site, where the same HTML adapts to screen size, this changes little: mobile and desktop are the same page.
Problems appear when the mobile experience serves less. The checks that matter:
- Same main content on mobile as desktop. Content collapsed in tabs or accordions is fine if it is in the HTML.
- Same headings, titles, and meta descriptions.
- Same structured data and the same image alt text.
- Crawlable mobile resources: CSS, JavaScript, and images not blocked in robots.txt.
- Lazy-loaded content that loads without requiring a user interaction such as a swipe or click.
Example
A store uses a separate mobile site at m.example.com that drops the long product description and reviews to keep pages light. Under mobile-first indexing, Google indexes the shortened page. The product loses rankings for long-tail queries that matched the description, even on desktop.
The fix is to serve the same content on mobile, ideally by moving to a responsive design with one URL per page.
In WordPress
Nearly all current WordPress themes are responsive, so the same HTML serves every device. Issues come from page builder settings that hide sections on mobile (hidden elements may still be in the HTML, but some builders remove them), mobile-specific plugins that serve a stripped theme, and missing viewport meta tags on old themes. Hydrogen SEO's site health score has a mobile area covering common theme issues; see site health score.
Common mistakes
- Hiding content or internal links on mobile to save space.
- Separate m-dot sites that serve less content or lack structured data.
- Blocking resources the mobile rendering needs.
- Intrusive interstitials that cover content on phones.
Common questions
Is there a separate mobile index?
No. Google has one index, and it is built primarily from the mobile versions of pages.
Do I need a separate mobile site?
No. Google recommends responsive design, which serves the same HTML at the same URL to every device and avoids most mobile-first issues.