Mobile-first indexing: adapting to the next era of mobile

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Indeed, mobile is the future of search. As of the fourth quarter of 2019, Google had the highest share of organic mobile search traffic with 61%.

It makes little to no sense at all to send people to pages optimized for desktop when they’re using mobile, right? Having in mind that search results are formulated mostly by a system that ranks desktop pages first, it‘s only natural that Google is revamping their entire algorithm to focus on mobile search.

It’s been a few years now that Google started working on mobile-first indexing. With mobile-first indexing, Google Search Engine primarily uses a page’s mobile content for creating its search index and ranking. You can view this timeline below:

  • November 4, 2016: Google have begun experiments to make their index mobile-first.
  • December 18, 2017: Google have started evaluating sites independently on their readiness for mobile-first indexing and transitioning them when ready.
  • March 26, 2018: Google have started migrating sites that follow the best practices for mobile-first indexing.
  • December 19, 2018: Google use mobile-first indexing for over half of the pages shown in search results globally.
  • July 28, 2019: Mobile-first indexing is enabled by default for all new, previously unknown to Google Search, websites starting July 1, 2019.
  • March 05, 2020: Google announced that they’ll be switching to mobile-first indexing for all websites starting September 2020.

Take a read to find out more about the impact of mobile-first index and how it has been affecting websites ever since.

Mobile share of organic search engine visits

What is mobile-first indexing?

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

Over the years, Google has provided us the following pieces of new information and updates about how mobile-first indexing works and how to prepare.

Mobile-first indexing simply means that instead of looking at the desktop version of the page, Google looks at the mobile version of the page first. For ranking and indexing purposes, that is.

Technically, no matter what device you use, Google will show you results from their mobile index.

What about the desktop version?

Pay attention that it’s called “mobile-first” and not “mobile-only” indexing. So this doesn’t mean Google is going fully mobile or creating a separate index for mobile and desktop results.

During Google Webmaster Central office-hours hangout from 23.08.2019 John Mueller (Webmaster Trends Analysts at Google Switzerland) has said that:

“Mobile usability is not the same as mobile-first indexing.”

Since pages without mobile versions still work on mobile devices, the lack of mobile-friendliness and not having a mobile-responsive layout doesn’t prevent from being indexed. However, such pages would lose a ranking boost for having poorer user experience in comparison to mobile-friendly ones.

Why does it matter?

For most sites, a switch from desktop to mobile-first index should be seamless. As a matter of fact, if your website was published after July 1, 2019, mobile-first indexing is already enabled by default.

This change nonetheless affects the rankings of websites that:

  • have never provided users with a flawless mobile experience
  • provide separate mobile and desktop pages for users, depending on which device they’re using. Especially, if there’s a significant difference between the desktop and mobile versions of the same page in terms of:
    • content
    • structured data
    • link profiles

Basically, it all comes down to the fact how your website and pages are optimized for mobile. This brings us to the next point.

Mobile version of your website

Website mobile version

Bear in mind that up until now the desktop site was considered the primary version and the mobile version was treated simply as an addition to your website.

But now, with mobile-first indexing, Google shifts the priority to the mobile version of sites, instead.

In reality, there are 3 different ways to implement a mobile version of your website:

  • “M-dot” Configuration
  • Dynamic Serving
  • Responsive Design

Each of them has its own perks, well, except maybe “m-dot” configuration (arguably, an outdated solution), but just for the sake of argument, let’s cover them all.

“M-dot” Configuration

This technique is also known as separate mobile URLs. In simple terms, visitors are directed to an optimized URL based on the device they use. Usually:

  • (for desktop users)
  • (for mobile users)

“M-dot” websites were once popular but are becoming a thing of the past. Of course, there are a number of reasons for this.

“M-dot” pages may cause SEO issues regarding “rel=canonical” and “rel=alternate” tags, and confusion in general, both from search engines and users. Not to mention, it takes at least twice as much effort to manage them all. So, it’s not recommended option.

Dynamic Serving

Contrary to “m-dot” configuration, dynamic serving websites utilize only one URL for each device that searches for your website. In this case, the server looks for the User-Agent value in the HTTP header to determine whether it is dealing with a desktop, tablet, or smartphone. Depending on the User-Agent value, the server then sends out different files (HTML, CSS, JS, media… you name it).

This means that the HTML structure of your website will vary on a device-by-device basis and the experience will be different.

Dynamic Serving has arguably the greatest potential for performance optimization because the mobile device doesn’t receive tons of surplus code and files.

Dynamic Serving for mobile

This is a great solution for e-commerce websites that are heavy on different kinds of interactions, but for regular blogs and sites? Not so much.

The biggest drawback of fully dynamic setups has to be the added maintenance – the more different the two versions are, the higher the maintenance costs will be.

Responsive Design

And last but not least there is Responsive Design.

Responsively designed website adapts to the size of the viewing window without a need for separate URLs or different HTML for each device. The content remains the same; the only major changes will be in the design of the website. In other words, your mobile and desktop pages are one and the same.

Sure, in this way, mobile devices have to load lots of unnecessary desktop content that they usually don’t even display and become slow(-er), but in terms of being SEO-friendly?

Google specifically recommends using responsive design for mobile websites.

Although each of these above-mentioned types of implementations works, Responsive Design is a good, general all-round solution to provide a decent visual experience for the users, while being SEO-friendly.

Mobile optimization

There’s no denying that mobile site has essentially become more important to Google than your desktop site. So if you still want to keep driving organic traffic, improving mobile optimization should be your top priority.

How to ensure that search engines consider your site optimized for mobile?

The first thing that you can do is head to the Google Search Mobile-Friendly Test and give it a try. Google will let you know if your site has any mobile usability issues.

Likewise, you can also use Google’s Mobile Usability Test in the Google Search Console and get a full report on this matter.

These tests focus mainly on user experience design, evaluation of font sizes, image and button properties, page loading times and other aspects.

Regardless of how the content is presented to your users, it should be nearly identical whether on mobile or desktop:

In particular, we recommend making sure that the content shown is the same (including text, images, videos, links), and that metadata (titles and descriptions, robots meta tags) and all structured data is the same. – John Mueller, Google Zurich.

Furthermore, it’s recommended to allow Googlebot to fully access and render all important parts of your site’s code, including Javascript. Unless Google can fully crawl your page, they can’t tell whether it’s mobile-friendly or not, and, because of this, your rankings could suffer.

Speed is the key

Nowadays, speed matters. When users search for information on mobile devices, they want to access it quickly which makes your site’s load time an integral part of the mobile experience. This isn’t just an important factor for your user experience; page speed is also one of the signals used by Google’s algorithm to rank web-pages. In fact, Google recommend that your site loads in under a second for mobile users.


Mobile-first indexing is Google’s another determined attempt to reflect user behavioral trends and establish refreshed standards for web development. It constitutes a major switch in how Google handles crawling, indexation and rankings – from being desktop-oriented to being mostly crawlable and indexable with mobile user-agents.

If you have a fully responsive site with mobile and desktop pages being one and the same, then you shouldn’t be affected by mobile-first indexing that much. In these circumstances, your main goal will be to properly optimize the mobile user experience. The content should be usable, fast, and appealing when it is presented on a mobile device.

In all other cases, additional changes may be required.