Check your log files to see if you see an increase in smartphone Googlebot activity, it may be a sign your site is now in the Google mobile first index.
Google has posted on the webmaster blog more advice around getting ready for the mobile-first index.
Google confirmed it has rolled out the mobile-first index “for a handful of sites” and said the search team is “closely” monitoring those sites for testing purposes.
You will know when your site moved over by checking to see a significantly increased crawling rate by the Smartphone Googlebot in your log files and the snippets in the results, as well as the content on the Google cache pages, will be from the mobile version of your web pages. Again, Google said only a small number of sites have migrated.
Gary Illyes from Google posted several tips to get ready for the mobile-first index:
- Make sure the mobile version of the site also has the important, high-quality content. This includes text, images (with alt-attributes), and videos — in the usual crawlable and indexable formats.
- Structured data is important for indexing and search features that users love: It should be both on the mobile and desktop version of the site. Ensure URLs within the structured data are updated to the mobile version on the mobile pages.
- Metadata should be present on both versions of the site. It provides hints about the content on a page for indexing and serving. For example, make sure that titles and meta descriptions are equivalent across both versions of all pages on the site.
- No changes are necessary for interlinking with separate mobile URLs (m.-dot sites). For sites using separate mobile URLs, keep the existing link rel=canonical and link rel=alternate elements between these versions.
- Check hreflang links on separate mobile URLs. When using link rel=hreflang elements for internationalization, link between mobile and desktop URLs separately. Your mobile URLs’ hreflang should point to the other language/region versions on other mobile URLs, and similarly link desktop with other desktop URLs using hreflang link elements there.
- Ensure the servers hosting the site have enough capacity to handle potentially increased crawl rate. This doesn’t affect sites that use responsive web design and dynamic serving, only sites where the mobile version is on a separate host, such as m.example.com.