Google’s mobile first index is Google’s pivot to using mobile versions of websites when it comes to indexing and ranking sites in the search results pages (SERPs). This has been a reflection of the increasing use of mobile phones to browse the web, access websites and, most importantly, search for sites and businesses using Google’s search engine.

Whilst it is not recommended to have separate mobile and desktop versions of the same site (as content can easily differ and this can be an issue) most modern CMS’s can generate a mobile ‘version’ of the original site using CSS which will adjust elements of the website’s design based on screen width. These are then placed for optimal display on a mobile or tablet (ie. a narrower portrait view for mobile devices). 

Whilst the mobile version will be displayed to mobile users and the desktop version displayed for desktop users, Google will only use the mobile version of the site when indexing. This has meant that websites that aren’t optimised for mobile, or don’t have mobile versions, are at a disadvantage in the SERPs compared to their mobile optimised peers.

The Mobile First Index Rollout

The move by Google to mobile first indexing is a reflection of the changing way in which people are using the internet, with the growth in the popularity of mobile devices such as smartphones and tablets now performing the majority of search queries conducted on its search engine. 

Google recognised this back as early as 2016. At this time, rankings and indexing were based entirely upon the desktop version of websites, which was frequently superior to the mobile version that was more commonly visited by internet users clicking through from their Google search. As a result, the rankings and indexing did not accurately reflect the experience of the majority of Google’s users.

Google’s mobile first index as a concept has been around since the end of 2017, when it was announced to be rolled out. In March 2018, Google announced that websites would need to prepare for a full rollout, but since July 2019 all new, or previously unindexed websites, have been subjected to Google’s mobile first index methods. 

Google initially planned to launch a full rollout to all websites in March 2020 but pushed this back to 2021, citing ‘uncertain times’ in a blog post.

There is no facility to opt in or out of mobile first indexing, which means that all websites must now be developed with a focus on the mobile experience equalling that of desktop users if they hope to be fully optimised for search across both platforms.

Where We Are Now

Now that it’s been a few years since Google first announced the mobile first index, Google has made the shift to predominantly using the mobile version of a site’s content for indexing and ranking, crawled with the smartphone agent Googlebot.

Mobile first indexing is enabled by default for all new websites, while older or existing websites are continuously monitored and evaluated based on the mobile first indexing best practices.

In January 2020, Google added to their mobile first indexing best practices a strong emphasis on giving users an identical experience both on mobile and desktop, creating a sense of harmony between the interfaces. This is crucial – not only does it make for a better user experience, but as Google is now almost completely only indexing the web using a smartphone Googlebot, which only indexes the mobile content.

In March 2021, Google’s John Mueller confirmed that when a site is shifted over to mobile first indexing, Google essentially drops everything that’s only on the desktop site and ignores it. Anything you want to have indexed therefore needs to be on the mobile site.

This included:

  • Using the same meta robots tags and meta descriptions on the desktop and mobile versions of the site.
  • Using the same content on the desktop and mobile versions of the site – including headings, written information, and images. You can, of course, use a different design on each interface to maximise the user experience for that specific screen or device – just make sure that the content on your mobile site is equivalent to the desktop site.
  • Making sure you use meta descriptions for your mobile desktop pages and keeping all metadata the same as the desktop pages.
  • Ensuring the desktop and mobile versions of the site have the same structured data.
  • Making sure Googlebot can access and render mobile and desktop page content and resources.

Takeaways for Business

As well as making sure all content is the same on your site’s mobile and and desktop version, focus on these key strategies to give your users the best mobile-friendly experience you can:


There are three configuration options you can use when creating a site for mobile devices:

  • Responsive design: This is the route that Google recommends taking, as it’s the simplest one to implement and maintain. This serves the same HTML code on the same URL, regardless of the device the user is accessing the site from, but it is able to display the content differently based on the screen size of the user’s device.
  • Dynamic serving: This uses the same URL, regardless of the device the user is accessing the site from, using functions such as user-agent sniffing to serve a different version of the HTML to different devices.
  • Separate URLs: This serves a different HTML to each device, using separate URLs. As with dynamic serving, this relies on the user-agent and HTTP headers to redirect the users to the version of the site appropriate for their device.

Access & Render

Ensure Google can access and render your mobile site, including all content and resources, by:

  • Using the same meta robot tags on each version of the site.
  • Google won’t load content that requires user interactions such as clicking, typing, or swiping, so make sure that you don’t lazy-load primary content upon user interaction.
  • Make sure Google can crawl your URLs and that you’re not blocking anything with the disallow directive.

Structured Data

If you use structured data on your site, it’s important to ensure it’s present on both the mobile and desktop versions to align with Google’s smartphone agent. Make sure the URLs used in the structured data on the mobile versions are updated to the mobile URLs.

Ad Placement

Ad placement can be a crucial factor in the quality of the user experience, and can also harm your mobile page ranking. Following the Better Ads Standard can help you avoid any errors and optimise the functionality of your mobile site.

Visual Content

For image and video best practices, Google recommends these tips and tricks:

  • Use high quality images – avoid low resolution images on your mobile site.
  • Use a supported format for images.
  • Don’t use URLs that change each time the page loads, as Google won’t be able to index your images properly.
  • Make sure all information is consistent across your mobile and desktop versions – this includes alt text, titles, captions, file names, and text.
  • For videos especially, make sure the visual content is in a good position on the page when viewed through a mobile screen, ie. the user doesn’t have to scroll too much to find the video.


Page speed has been cited as a crucial factor to consider when optimising the user experience on any device, but it is even more important with the mobile first index update.

Separate URLs

If you’re using separate URLs for the desktop and mobile version of your site (ie. the m-dot URL for the mobile site), it’s important to ensure that:

  • The error page status is the same on both the desktop and mobile sites.
  • The mobile site doesn’t contain fragment URLs.
  • You verify both versions of your site in Search Console so that you have access to both versions’ data.
  • The mobile version of your site has enough capacity to handle an increase in crawl rate, should that occur.
  • You verify your robots.txt directives work the way you want them to for both your mobile and desktop site.