From the 2016 announcement to smartphone-only crawling
Advice to prepare for mobile-first indexing is out of date; the switch is done. The timeline:
2016. Google noted that its ranking systems still typically evaluated the desktop version of a page, even though most searches were on mobile.
2019. Google enabled mobile-first indexing by default for all new websites, previously unknown to Google Search, starting July 1, 2019.
2023. The move was declared complete.
2024. Google said that after July 5, 2024 it would crawl and index the remaining desktop-crawled sites with Googlebot Smartphone only.
Google stated that a site whose content is not accessible at all on a mobile device would no longer be indexable. That does not mean a separate mobile version is required: Google says content can be included in its Search results without one (though it strongly recommends one).
What it looks like in server logs
Each request carries a
User-Agentheader that identifies the crawler type: Googlebot Smartphone or Googlebot Desktop.Desktop requests do not disappear: Google still uses Googlebot Desktop for some crawls, such as product listings and Google for Jobs.
Googlebot Smartphone and Googlebot Desktop share one robots.txt user agent token, so robots.txt cannot target only one of them.
Parity checks for m-dot and dynamic serving sites
Google recommends responsive web design, which serves the same HTML on the same URL to every device, as the easiest pattern to implement and maintain. One HTML for every device means there are no two versions to drift apart. The checks below matter when phones get different HTML, through dynamic serving or a separate m-dot URL.
Metadata. Google asks for the same structured data, title elements and meta descriptions on the mobile and desktop versions.
Robots rules. Google asks sites with separate mobile HTML to use the same meta robots tags on the mobile and desktop versions.
Hidden content. Google does not load content that needs a user interaction such as swiping, clicking or typing. Google accepts accordions or tabs that save space on mobile; what it asks is that the content is not removed from the mobile page.
Parity here means content and markup. Page speed and mobile usability are separate topics.
For technical SEO on a Next.js site, see Next.js SEO optimization. For general build practices, see web development best practices.
Sources
- Mobile-first Indexing Best PracticesGoogle · developers.google.com
- Mobile-first indexing (Google Search Central Blog, 2016)Google · developers.google.com
- Mobile-first indexing has landed - thanks for all your support (2023)Google · developers.google.com
- Mobile-First Indexing by default for new domains (2019)Google · developers.google.com
- Mobile-indexing-vLast-final-final.doc (2024)Google · developers.google.com
- What Is GooglebotGoogle · developers.google.com