Mobile-first indexing means that Google uses the mobile version of a site’s content, crawled with the smartphone user agent, for indexing and ranking. Google runs a single index, and that index is built from the mobile content.
At a glance
- Type
- Google indexing approach (the mobile version of a page is the basis)
- Affects
- indexing and ranking
- Since
- announced 2016, declared complete on Oct 31, 2023
Last checked:
What does it mean for SEO?
Content that appears only on the desktop version can be missing from the index. Google announced in March 2020 that it would apply mobile-first indexing to the whole web, and declared the move complete on October 31, 2023. The remaining sites have been crawled with the mobile Googlebot since July 5, 2024. Its documentation lists these points:
- Mobile and desktop show the same primary content. Collapsed sections such as tabs or accordions are fine.
- Structured data is present on both versions, starting with Breadcrumb, Product and VideoObject.
- Titles and meta descriptions match.
- Robots meta tags are the same on both versions.
- Primary content is not lazy-loaded behind interactions, since Google does not click, swipe or type.
- Images and videos keep consistent alt text and supported formats.
| Configuration | URL | HTML | Technical signals | Google's position |
|---|---|---|---|---|
| Responsive design | same URL on every device | same HTML; the layout adapts to the screen size | none needed; content and metadata are identical on mobile and desktop | recommended as the easiest pattern to implement and maintain |
| Dynamic serving | same URL on every device | different HTML per device, chosen by user-agent detection | Vary: user-agent response header | supported; the mobile version needs the same content as desktop |
| Separate mobile URLs | a separate URL per device, e.g. m. | different HTML per device | mobile page: rel="canonical" to the desktop URL; desktop page: rel="alternate" with media to the mobile URL; redirects based on user agent and Vary | supported; the desktop URL is always canonical, and hreflang links mobile to mobile and desktop to desktop |
Google uses the mobile version of a page, crawled with the smartphone agent, for indexing and ranking (mobile-first indexing). Only the content shown on the mobile version is used for indexing. Google's best practices on signals and content parity apply to dynamic serving and separate URLs only; with responsive design, content and metadata are the same anyway. Sources: Google Search Central: Mobile site and mobile-first indexing best practices (last updated 2025-12-10); MDN: Vary header. Last checked: .
- Google adds a “mobile-friendly” label to mobile search results. It appears for pages that are readable without zooming and avoid Flash.Source: developers.google.com
- Google announces that it will expand its use of mobile-friendliness as a ranking signal for mobile searches from April 21, 2015.Source: developers.google.com
- The mobile-friendly update starts rolling out globally, unofficially called “Mobilegeddon”. It only affects rankings on mobile devices.Source: developers.google.com
- Google removes the “mobile-friendly” label because 85% of pages in mobile results now carry it. Mobile-friendliness remains a ranking signal.Source: developers.google.com
- Google announces mobile-first indexing and starts experimenting. In future, mainly the mobile version of a page is to be used for indexing and ranking.Source: developers.google.com
- After a year and a half of testing, the migration begins. Google first moves sites that follow the best practices.Source: developers.google.com
- Mobile-first indexing becomes the default for all new websites previously unknown to Google Search.Source: developers.google.com
- Google announces that all websites will switch from September 2020. At this point 70% of sites shown in search results have already moved.Source: developers.google.com
- Google postpones the complete switch to the end of March 2021.Source: developers.google.com
- Google declares the move to mobile-first indexing complete. A small set of sites that do not work on mobile is still crawled with desktop Googlebot for now.Source: developers.google.com
- The Mobile-Friendly Test and the Mobile Usability report in Search Console are retired.Source: developers.google.com
- As the final step, Google crawls the remaining sites with the mobile Googlebot after this date. Content that is not accessible on mobile devices at all can no longer be indexed.Source: developers.google.com
Google itself does not use the name “Mobilegeddon”; it comes from the SEO industry. The planned dates of September 2020 and March 2021 were not met; according to Google the switch was only completed in October 2023. Last checked: .
Example
A product page on desktop has a table of technical specifications. The mobile version hides the table and does not load it at all. Google indexes the mobile version, so the specifications can be missing from the index.
Common questions
Is there a separate mobile index? No. Google keeps one index and builds it from the mobile version.
Does mobile-first mean a site is mobile-friendly? No, it describes which version Google reads. How usable the site is on a phone is a separate topic.
Sources
- Mobile-first indexing best practices – Google Search Centraldevelopers.google.com
- Announcing mobile first indexing for the whole web – Google Search Central Blog (2020)developers.google.com
- Mobile-first indexing has landed – Google Search Central Blog (Oct 31, 2023)developers.google.com
- Rolling out mobile-first indexing – Google Search Central Blog (2018)developers.google.com
- Mobile-first indexing, final step – Google Search Central Blog (2024)developers.google.com
Last updated: