A marketer’s guide to mobile-first indexing

Rob Barnes

SEO Manager

There’s no question that mobile search has taken the digital marketing world by storm, and with it, comes new ways of thinking. In Google’s ever-continuing efforts to follow user trends and make the web more mobile-friendly, mobile-first indexing was devised. So, you may have heard of it but if you’re wondering what mobile-first indexing means for you, read on to find out what it is and how you can use it to it’s best ability for marketing and website success. 

What is mobile-first indexing and why?

First thing’s first, what is mobile-first indexing and why has it been introduced? 

Mobile-first indexing does what it says on the tin. The search engine will evaluate your site based on the mobile version. This is to mirror the growing trend of mobile users versus desktop users. In essence, this means that if you have content on your desktop site but not on your mobile site it will not count towards your Organic performance. It is therefore important to closely review your site as if you were a mobile user and ensure your content meets the standard.

Ever since web browsing capabilities were first introduced on mobile phones, more and more people adopted the technology. With the continual improvement of the capabilities of mobile devices and faster network speeds, it took a mere 7 years to go from 100% desktop usage to under 50%.


While users were moving over to mobile devices in droves it appeared that webmasters were not following suit. Many sites had separate mobile sites that had much-reduced capabilities when compared to their desktop sibling. These mobile websites would often comprise of just a handful of pages and little textual content. The reason for this was to cater to the poorer network capabilities of the early 2000s. While this made sense from a technical perspective, these sites offered very little context to search engines and therefore could not be relied upon for ranking signals.

So ultimately, there was a disconnect in user behaviour and websites serving those users. Seeing this trend, Google started a push towards mobile-first indexing to force webmasters to focus on its mobile users. As of July 2019, any new websites were going to be crawled using Google smartphone user agent, and as of September 2020, this user agent was enabled for all websites. 

This forced webmasters to pay closer attention to their mobile sites and ensure that the mobile experience was comparable to that of a desktop user.

So here we are, we live in a world where all websites are crawled using the Google Smartphone user agent. This means that it doesn’t matter how great your desktop site is, Google will determine how your site ranks based on the mobile site.

So, what do I need to do?

Firstly, you need to know what type of site you have when it comes to responding to users on mobile devices. There are three main methods. 

  1. Separate mobile site: All mobile content sits on separate URLs (usually m.domain.com or mobile.domain.com) and the mobile users are directed to the appropriate site based on the type of device they are using.
  2. Dynamic serving: All content sits on the same URLs but different HTML is served based on the user’s device type.
  3. Responsive design: All content sits on the same URLs and the same HTML is also served. Design elements change to respond to different screen sizes. 

Google prefers sites to utilise the responsive method as there will be good consistency between the content and capabilities of the desktop and mobile sites. Fortunately, the vast majority of sites are responsive. If you are still utilising one of the other methods then don’t worry, your site(s) can still perform well in a mobile environment; it is just important to be aware that Google is looking for consistency across your desktop and mobile offerings and therefore, content, metadata and technical mark-up should be the same for all users. 

Next, using a mobile, browse your own website. How is the experience? Are you able to easily navigate the site and achieve the types of things that you’d want users to do? If so, that’s great, you’re on the right tracks. If not, there are some improvements to make.

To get a little more scientific about it, there are a variety of tools out there that can help you understand if your site is mobile friendly. To start with, check out the Google mobile-friendly test which will give you a quick indication of whether Google sees the page as technically optimised for mobile users. It is important to note that just because the report says the site is mobile-friendly, it doesn’t mean it can’t be made even better.  

Next, if you have Google Search Console, check out the Mobile Usability report. If you don’t have Google Search Console, you can set it up for your site now. It’ll provide you with loads of great insight into how Google sees your site and the problems it encounters. 

The mobile usability report provides a top-level view of the types of issues that are affecting the site, and also includes sample URLs for each issue. The report also provides recommendations on how to resolve these issues. 

Lastly, and getting a little more technical, the Lighthouse report in Google Chrome can provide further insight into specific mobile usability issues, all detailed within the SEO section of the report.

This tool is hidden within the dev tools in Google Chrome so you’ll first need to navigate to the page you want to run the report on. Once there, hit F12 to access dev tools, find the Lighthouse option and then run the report.  

So, you’ve made your site mobile friendly and you’ve passed every test out there. Does that mean your site is going to stay at the top of the rankings forever? We’re afraid not.

The technical side of being mobile-friendly is only part of the battle. It is important to ensure that the content of the mobile version of your site also meets the grade. You probably have a responsive site and therefore the content should be the same for both desktop and mobile users. However, you have much less real estate to play with on a mobile device, and as such content often gets hidden away and functionality gets removed. This is where marketing and SEO teams tend to knock heads, as the SEOs want all of the content visible for search engines and the marketing teams want the content to be streamlined and efficient for the user. Luckily there is a compromise through the use of accordions. An accordion hides the content until the user taps to expose the content, which is then revealed. The content is still available for Google to review while keeping a “clean” design for users. 


To summarise, people will be browsing your site on mobile devices and will expect a comparable experience to desktop. Google has reacted to this by evaluating websites based on its mobile version. There’s a wealth of tools out there to help you ensure that you are mobile-friendly from a technical perspective. As marketers, you need to ensure consistency of experience across all device types.

If you want some help on getting to grips with optimising for mobile, give us a shout

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