As exciting as new developments in voice search or better online shopping may be, the talk in the SEO and digital marketing world for much of the last several months has focused on the next big change from Google: a full rollout of the mobile-first index, which aims to improve user experience in search by using a site’s mobile version as the basis for its rankings in search results. Because of this, it will be the content and structured data on the mobile site that shows up in search results, in addition to determining where it ranks.

This change is a significant update to Google’s past algorithm changes intended to reward mobile-friendliness, and seems to have been released at a time when most websites have had ample time to ensure they comply with Google’s standards. It is consistent with an overall move on their part toward a mobile-first web, which seems all but inevitable given the near-complete takeover of mobile as the predominant platform for web use today.

When Did The Mobile-First Index Hit?

Google first announced the coming change to its search index back in November 2016, and reported last December that it had begun the process of indexing select sites using its mobile-first method. But near the end of last month, they announced a new update: some sites across the web are officially being migrated to mobile-first indexing.

Google has clarified that the process of indexing sites this way does not mean there is a separate mobile-first index – there is still just one Google search index. The difference is that certain (and eventually all) sites are having the mobile versions of their sites crawled, whereas historically it has always been the desktop version that provided the basis for Google search results.

When Will All Sites Be Indexed Mobile-First?

Google hasn’t declared a formal timeline for this process, or when they expect to index all sites in this manner. As is usually the case with adjustments to their algorithm, expect to see a gradual rollout in select areas and for select websites, with fluctuations from time to time as the kinks get worked out.

As much as this may seem scary from an SEO perspective, changes like this have simply become a fact of life with Google, and are mostly unsurprising given Google’s consistent mission of improving user experience and the role they see played by mobile-friendliness. Ultimately this update will more than likely encourage website owners and developers to improve the quality of their platform and make their sites more helpful for all users – which benefits everyone in the end even if the transition brings some short-term changes.

If you are concerned about how to prepare your site for mobile-first indexing, I’ve included some resources below. This adjustment should not dramatically affect websites that already use a modern mobile-friendly design, but it’s helpful to know exactly what Google will be looking for when crawling your mobile site.

For reference, here are the criteria Google originally listed for their mobile-first evaluation process:

  • 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.

Some other helpful resources:

This FAQ from SearchEngineLand, while a couple years old, is a useful guide to the basics of mobile-first indexing as originally explained by Google. https://searchengineland.com/faq-google-mobile-first-index-262751

Here are Google’s recommended best practices for developers: https://developers.google.com/search/mobile-sites/mobile-first-indexing

Google’s mobile speed test tool: https://testmysite.thinkwithgoogle.com/

And the mobile-friendliness test tool: https://search.google.com/test/mobile-friendly