Definition
Mobile-first indexing is Google's indexing method that uses the mobile version of a site as the primary version for indexing and ranking. Since July 2019 for new sites and 2021 for the entire web, Google has moved to full mobile-first indexing. This means that if your site has different content between mobile and desktop versions, it is the mobile version that will be considered for ranking. Sites not optimized for mobile risk ranking degradation. Best practices include responsive design, mobile/desktop content parity, verifying that structured data and meta tags are present on the mobile version, and optimizing mobile loading speed via Core Web Vitals.
Key Points
- Google uses the mobile version as primary reference since 2021
- The mobile version's content is what gets indexed
- A non-mobile-optimized site risks losing rankings
Practical Examples
Content hidden on mobile
A site hides important text blocks on mobile via CSS display:none. Google no longer indexes this content, resulting in a 30% organic traffic loss.
Unconfigured viewport
A site without a meta viewport displays the desktop version on mobile. Google considers it non mobile-friendly and penalizes it in mobile results.
Frequently Asked Questions
Use the URL Inspection tool in Search Console. If Google crawls your site with Googlebot Smartphone, you are on mobile-first indexing.
Yes, but Google uses mobile Googlebot to crawl it. If the site is not accessible on mobile, rankings can suffer significantly.
Go Further with LemmiLink
Discover how LemmiLink can help you put these SEO concepts into practice.
Last updated: 2026-02-07