Performance & Core Web Vitals · Glossary term

Mobile-first indexing explained without jargon.

Since 2021, Google uses the mobile version of the page as primary for indexing. If your site isn't responsive, you have a big problem.

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Extended definition

Since 2021, Google uses the mobile version of the page as primary for indexing. If your site isn't responsive, you have a big problem.

Context and application

Mobile-first indexing doesn’t mean “mobile-only” — Google still crawls desktop, but prioritizes the mobile version for indexing and ranking decisions. Common mistakes: content that appears only on desktop (hidden on mobile with display: none), structured data missing on mobile, internal links differing between mobile/desktop. Correct tactic: same content, same link structure, only adapted layout. Verification in Google Search Console “URL Inspection” → shows what mobile vs desktop crawler saw.

Related terms

Indexing, Core Web Vitals.

Rest of the glossary

The SEO Master PRO MAX glossary has 58 essential terms, organized in 7 categories (Audit & Technical SEO · Content & On-page · Performance & Core Web Vitals · Backlinks & Authority · AI & Search 2026 · SERP, Schema & Rich Results · Privacy & Compliance). All with clear definitions, extended context, concrete examples.

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