Mobile-first indexing means Google predominantly uses the mobile version of a website’s content for indexing and ranking, rather than the desktop version. Google made this the default approach for all websites, reflecting the reality that most searches now happen on mobile devices.
This makes it critical that a site’s mobile version contains the same content, structured data, and internal links as its desktop version — historically, some sites offered a stripped-down mobile experience that omitted content available on desktop, which under mobile-first indexing can directly harm rankings.
With responsive design (where the same HTML and content adapt to different screen sizes) now the dominant approach for most modern websites, mobile-first indexing issues are less common than in the past, but remain an important check for sites with separate mobile URLs or older designs.
Mobile-first compliance is verified as part of our Technical SEO audits.