April 2018

In early November of last year, Google announced their imminent move to “Mobile-first Indexing.” This announcement served as an initial confirmation that the mobile-first index migration experimentation process had progressed beyond testing, though a timeline for migration beyond carefully selected sites was still unconfirmed.

On March 26th 2018, Google provided an updated announcement: they have begun migrating sites that currently follow the mobile-first indexing best practices to the “mobile-first” index. This recent announcement is the first confirmation that the scope and quantity of sites being migrated had increased and that regular and ongoing rollouts could be expected by webmasters moving forward.

Webmasters will be notified via Google Search Console whether their site has been migrated and enabled to the mobile-first index. Additionally, webmasters will see a significant increase in the crawl rate via the smartphone Googlebot as the website is being migrated, as well as displayed mobile versions of cached pages in search results as soon as the website is indexed.


Google search engine page displayed on a mobile phone.


What is a Mobile-first Index?

Historically, Google has evaluated and ranked sites based on the desktop version of their webpages. As the mobile user-base grew, Google added in mobile-specific algorithm components to give preference to “mobile-friendly” websites within mobile search results, but on-page signals and content evaluation continued to utilize desktop pages.

With the majority of searches now being completed on mobile devices, the disadvantages of using a rank model based on desktop pages have increased. This is because some websites serve content differently to mobile users. Most often, this involves using truncated content on mobile, while serving more robust content to desktop users. This has the potential to create an experience gap between Google’s expected result and the mobile user.

In Google’s Mobile-first Index, mobile pages will now be stored, and on-page signals will be evaluated against these page versions. Desktop pages will still be served to desktop users, but will no longer serve as the basis for rankings.


Group of young people discussing what they are reading on their mobile devices.


Who/What Will Be Impacted?

The full scope of the impact is unknown, but statements made by some prominent Googlers’ indicate that the goal of initial experimentation is to limit the visible impact of the change. Based on available information, mobile configuration will be the determining factor for impact, with 4 distinct variations:


1.   Websites that currently utilize responsive design or dynamic serving as a mobile solution should see minimal impact, as long as primary content and markup is equivalent across mobile and desktop.

2.   Websites with a full mobile experience on a separate configuration, such as website.com or website.com/mobile/, should see minimal impact, as long as primary content and markup is equivalent across mobile and desktop. Additional steps such as Search Console verification and mobile robots.txt access may be required ensure full visibility remains.

3.   Websites with an altered or reduced mobile experience have the highest chance for negative impact to visibility, potentially in both mobile and desktop organic results. Measures should be taken to ensure that mobile page versions reflect all primary content and structured data markup.

4.   Websites without a mobile experience (desktop-only) will still be indexed, but the impact to search visibility is unknown at this point. Google has stated the following regarding desktop-only sites:

If you are building a mobile version of your site, keep in mind that a functional desktop-oriented site can be better than a broken or incomplete mobile version of the site. It’s better for you to build up your mobile site and launch it when ready.”


Woman sitting on a park bench reading a mobile-optimized travel blog website.


What are the Main Considerations?

1.      Content

  • Google will only index and evaluate content served to their mobile Googlebot. Mobile content should be evaluated to ensure that primary elements are displayed on mobile and accessible to Google.
  • As part of this change, Google intends to give full weight to collapsible, “accordion” content, as well as tabbed content. Previously, these types of content held diminished value.

2.     Page Elements

  • Important on-page elements, such as Title Tags, H1 tags, and internal links, are often treated differently on mobile sites, and may need to be optimized in a different way. This includes making sure the H1 tags are not hidden and important internal links in the main navigation and contextual content are still accessible by users and search engines.
  • Structured data is sometimes removed from mobile pages in order to speed up load times. If this is the case, applicable structured data will need to be added back to mobile pages to ensure that rich snippets are not lost. Additionally, Google recommends reducing the amount of structured data on pages in total:

“When adding structured data to a mobile site, avoid adding large amounts of markup that isn’t relevant to the specific information content of each document.”


If you want to learn about how Google is making the switch to mobile-first indexing, or how it could impact you or your clients, contact our expert SEO team today.




Paul Rasp is an SEO Supervisor for Response Mine, helping plan and execute strategy to improve clients’ visibility in Organic and Local search. His favorite part of the job is the opportunity to combine creative and analytical skills to find unique solutions to complex problems. He was voted “Most Likely to Have a Pun in the Oven” by everyone that’s ever met him and lives in an Atlanta United Five Stripes jersey.
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