Mobile-first indexing is Google's practice of using the mobile version of a page as the primary source for indexing and ranking. Google switched to mobile-first as the default in 2019. AI engines increasingly follow similar mobile-priority indexing. Sites must ensure the mobile version contains all content, structured data and meta tags identical to (or better than) the desktop version.
If you hide content on mobile (collapsing FAQs into accordion, removing details), Google indexes the hidden version. If your mobile version lacks schema that desktop has, you lose the schema benefit. Mobile parity is non-negotiable.
Use Google's Mobile-Friendly Test. Use Search Console's URL Inspection on mobile user-agent. Compare your mobile and desktop HTML responses to confirm parity in content, schema and meta tags.
Mobile viewport meta tag. Responsive design (no separate m-dot subdomain). All content visible on mobile (no display:none for crawlable content). Same schema markup on both viewports.
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