Ever since Google first announced that it was experimenting with mobile-first indexing in 2016, there has been a ton of information published.

Throughout the years, Google has given us bits of new information and updates about how mobile-first indexing works and how to prepare.

The following is a compilation of things we know, so far, about Google’s mobile-first indexing.

There Is No Separate Index for Mobile

Out of all the things listed about mobile-first indexing, this one is widely known.

However, it is widely known to those of us in the search community, but it is still a confusing concept to those who are not in our industry.

Just to ensure there is no misunderstanding, Google has stated that there is not a separate mobile-first index.

Instead, mobile-first indexing means Google primarily uses the mobile version of the webpage for ranking and indexing purposes.

In 2018, Google explained that with mobile-first indexing, the URL of the mobile-friendly version of your site is indexed.

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If your website has separate mobile and desktop URLs, Google shows the mobile URL to mobile users, and the desktop URL to desktop users.

However, regardless, the indexed content will be the mobile version.

You Can’t Force a Move to Mobile-First Indexing – You Also Can’t Opt Out

At the end of 2017, Google announced that they would start slowly rolling out mobile-first indexing. By March 2018, Google stated that they were expanding the rollout and instructed websites to prepare.

As of the date of this article, though, not all websites have been enabled for mobile-first indexing. In August 2019, John Mueller encouraged site owners to be patient because eventually their sites would be moved over.

Martin Splitt, who works in Google’s Developer Relations, explained that there is no way to know exactly when a website will be moved to mobile-first indexing and at the same time, there isn’t anything you can do to make the process happen quicker.

Similar to not being able to force your website to be moved to mobile-first indexing, you also can’t opt out.

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Google decides the readiness of a website for mobile-first indexing based on the parity of text, links, images, and videos, as well as structured data and other metadata.

Mueller also warned website owners a while back that using a lot of JavaScript may prevent a website from being moved to mobile-first indexing.

If you are using an app interstitial to replace your site’s homepage, then that’s also going to be problematic, according to Mueller.

Webmasters will be notified in Search Console when Google determines the site is ready for mobile-first indexing.

You can hear Mueller’s and Splitt’s explanation about when sites are moved to mobile-first indexing in the video below, starting at the 25:08:

“It can take a while. There’s another question [in the queue] that asks how can I switch to mobile Googlebot. There’s no way to opt in or out, we’re just progressively changing or moving sites to mobile-first indexing but there’s no way to tell you “oh yeah, next week it’s going to be you.” Be patient. It’ll happen. It’ll be fine.”

Mobile-First Indexing Is Applied to New Websites by Default

If your website was published after July 1, 2019, by default mobile-first indexing is enabled. Google made this announcement in May 2019 and explained that the change applied to websites that were previously unknown to Google Search.

The announcement went into detail about why Google would make mobile-first indexing the default for new websites.

According to Google, after crawling the web with a smartphone Googlebot over the years, they concluded that new websites are typically ready for this type of crawling.

Unlike websites published before July 1, 2019, Google does not notify webmasters in Search Console that the site is ready for mobile-first indexing.

Websites Should Provide the Same Experience on Mobile & Desktop

Google added to their mobile-first indexing best practices in January 2020 and the big emphasis was on providing an identical experience on mobile and desktop.

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Matt Southern provided a great summarized list of what Google meant by the same experience:

Ensuring Googlebot can access and render mobile and desktop page content and resources.

Making sure the mobile site contains the same content as the desktop site.

Using the same meta robots tags on the mobile and desktop site.

Using the same headings on the mobile site and desktop site.

Making sure the mobile and desktop sites have the same structured data.

Google warns that if you purposefully serve less content on the mobile version of a page than the desktop version, you will likely experience a drop in traffic.

The reason? According to Google, they won’t be able to get as much information from the page as before (when the desktop version was used).

Instead, Google recommends that the primary content on the mobile site be the same as the desktop site. Google even suggests using the same headings on the mobile version.

Mobile Usability Is Not the Same as Mobile-First Indexing

If Google can crawl the text on your website, and that text can be displayed on a mobile device, then your website can be added to mobile-first indexing.

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In January 2019, Mueller explained that if your content does not pass the mobile usability test, it can still be moved to mobile-first indexing. Even if Search Console’s “mobile usability” report shows that your site has valid URLs, it doesn’t mean those pages are ready for mobile-first indexing.

Mobile usability is “completely separate” from mobile-first indexing according to Mueller. Consequently, pages can be enabled for mobile-first indexing even if they’re not considered usable on a mobile device.

Therefore, you should not use Google’s mobile usability test, or the mobility usability report in Search Console, as a signal that your website is ready for mobile-first indexing.

You can hear Mueller’s explanation in the video below, starting at the 41:12 mark.

“So, first off, again mobile usability is completely separate from mobile-first indexing. A site can or cannot be usable from a mobile point of view, but it can still contain all of the content that we need for mobile-first indexing. An extreme example, if you take something like a PDF file, then on mobile that would be terrible to navigate. The links will be hard to click, the text will be hard to read. But all of the text is still there, and we could perfectly index that with mobile-first indexing. Mobile usability is not the same as mobile-first indexing.”

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In summary, mobile-friendliness and mobile-responsive layouts are not mandatory for mobile-first indexing. Since pages without mobile versions still work on mobile device, they are eligible for indexing.

Google Publishes (& Updates) Mobile-First Indexing Best Practices

Google provides a list of best practices for mobile-first indexing “to make sure that your users have the best experience.”

Most of the information Google shares as best practices are not really new. Instead, the list is a compilation of various recommendations and advice that Google has provided elsewhere over the years.

In addition to the list of recommendations above about creating the same experience on mobile and desktop, some of the other best practices include:

Making sure Google can see lazy-loaded content.

Making sure Google can crawl your resources.

Using the same metadata on the mobile and desktop site.

Making sure your ads don’t cause a bad mobile user experience.

Providing high quality images on the mobile site.

Using a supported format for images and videos.

Using the same alt text on the mobile and desktop site.

Avoiding video and image URLs that change every time the page loads on the mobile site.

Making sure videos are easy to find and view on the mobile site.

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Google has an entire section of the best practices document focused on suggestions for separate URLs. Here is a short list, but you can view all of the recommendations in Google’s best practices for mobile-first indexing document.

Making sure the error page status is the same on the mobile and desktop sites.

Avoiding fragment URLs in the mobile site.

Making sure the desktop pages have equivalent mobile pages.

Verifying both the mobile and desktop sites in Search Console.

Checking hreflang links on separate mobile URLs.

Making sure the mobile site can handle an increased crawl rate.

Making sure the robot.txt directives are the same on the mobile and desktop sites.

Google also has a Troubleshooting section of the best practices document, which is worth checking out.

It includes common errors that can either cause your site to not be ready for mobile-first indexing or could lead to a drop in rankings once your site is enabled.

Google Provides a Changelog on Mobile-First Indexing

Google published a changelog in its Mobile-first indexing best practices that gives a quick recap of the changes since 2016. You can view this changelog below.

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Stay Updated on Mobile-First Indexing

As you can tell, there is a lot on mobile-first indexing and more will be released.

Make sure you are staying on top of best practices and monitoring the health of your website in Search Console.

More Resources:

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