The Author
Rachel Costello

Rachel Costello is a Technical SEO & Content Manager at DeepCrawl. You'll most often find her writing and speaking about all things SEO.

Read more from Rachel Costello

DeepCrawl’s Ultimate Guide to Google’s Mobile-first Index

We’ve all talked (and worried) about it for a long time now, but Google’s shift to mobile-first indexing is finally rolling out… but, what exactly do you need to do to get your website ready?

At DeepCrawl, we launched a comprehensive mobile-first white paper to answer all of your questions, as well as explain exactly what you need to do to make sure your website can benefit from mobile-first, rather than suffer from it.

DeepCrawl's Ultimate Guide to Google's Mobile-first Index

Take a Look at Our Mobile-first PDF

For those of you who haven’t had a chance to read the guide yet, here are some of the key mobile-first topics that you should know about.

A lot has changed since Google’s first announcement

It feels like we’ve been talking about mobile-first for a long time, because, in reality, we have. It was first announced by Google’s Gary Illyes at Pubcon back in October 2016, and since then, a lot of new information has surfaced and Google has had to clarify a fair bit of confusion around mobile-first.

Here are some of the key developments since the first announcement:

There won’t be a separate mobile index

There won’t be a separate desktop and mobile index which will be maintained side by side. Google will only have one index which will be a combination of mobile-indexed content and desktop-indexed content, with the former starting to phase out the latter.

Google is sending out notifications when switching sites to mobile-first

We were originally told that the only way we could check for the indexing switch was to monitor Googlebot Smartphone activity in your log files and checking whether Google is caching your desktop or mobile content for a page. However, it was later announced that we’d receive notifications in Google Search Console when our sites are being switched.

Mobile content will be indexed for the mobile and desktop versions of a page

Mobile-first indexing means that whatever content appears on the mobile version of a page will be indexed for the desktop version too. This is why content parity is crucial, as whatever content is missing on your mobile-configured pages won’t be indexed.

Here are just a few of the other key topics that are discussed in our PDF guide.

What is mobile-first indexing?

Here’s how Google defines mobile-first indexing:

“Although our search index will continue to be a single index of websites and apps, our algorithms will eventually primarily use the mobile version of a site’s content to rank pages from that site, to understand structured data, and to show snippets from those pages in our results.”

Google’s index will now focus on mobile pages, and desktop pages will be phased out where there is a mobile alternative.

The appearance of SERPs will remain unaltered, but one of the main changes we will see is the way Google crawls and accesses websites in order to find their content.

Why is Google moving towards a mobile-first index?

Nearly 60% of all searches are now on mobile. The majority of users are now using mobile devices, therefore, Google is tailoring its services to its users by prioritising mobile pages. Google recognises the dominance of mobile and wants to bridge the gap that exists between mobile users and the previous desktop-first indexing system. The mobile-first index aims to do away with disjointed user journeys on mobile.

Basically, Google is launching mobile-first indexing for a mobile-first world.

What are the key considerations for mobile-first?


One of the resounding points around mobile-first is to ensure content is consistent across desktop and mobile. This applies to:

  • Textual content
  • Metadata
  • Images
  • Alt attributes

If you’re missing a key piece of content that you were ranking for with desktop-first indexing, Google won’t be able to rank that page anymore if it is being indexed mobile-first and the mobile version is missing that content.

Internal Linking

The key thing to bear in mind around internal linking on the mobile version of your site is accessibility for users and search engines, and whether you’re making it harder for them to get to particular pages due to reduced internal linking within your mobile configuration.

Internal linking doesn’t have to be identical between desktop and mobile, but it does have to be accessible.


Responsive is the easiest configuration for correctly implementing hreflang for mobile-first indexing, however, if you don’t have responsive design you’ll need to make sure mobile URLs point to mobile URLs, and desktop URLs point to desktop URLs.

Structured Data & Video

Markup and onsite videos should be consistent across desktop and mobile for ranking purposes, and they also need to be crawlable and indexable. You have to move everything you want to rank for across to your mobile configuration, not just textual content.

Page Speed

The latest updates from Google, including the upcoming ‘Speed Update‘ in July, enforce the point that mobile page speed is a huge focus for them, and it should be one our main priorities as digital marketers.

If you want to learn more about site speed and performance and how to make sure your site is optimised in the best way for your users, make sure you read our latest white paper on site speed.

How to Check Whether Your Site is Prepared

Bypassing even the smallest issue can cause huge repercussions in the SEO world, so luckily we’ve thought of everything else that can possibly be a hindrance to your website during the indexing change.

For Responsive Sites:

  • Make sure no important resources are being blocked such as images, JS & CSS
  • Check for legacy issues such as existing dynamic mobile pages or separate mobile pages that exist alongside your responsive site – these will be indexed instead of the responsive page!

For Dynamic Sites:

  • Include all important desktop content and markup on the mobile version of the page
  • Check that the vary: user agent HTTP header is in use
  • Make sure the right user agent is being served the correct version of a page

For Separate Mobile Sites:

  • Include all important desktop content and markup on the mobile version of the page
  • Maintain existing links between desktop and mobile pages and existing rel=canonical and rel=alternate setup
  • Guide the mobile and desktop user agents to the correct page version with 301 redirects
  • Make sure your servers have the capacity to handle increased crawl rate from Googlebot Smartphone
  • Make sure the mobile version of your site is verified in Search Console as well as the desktop version

For All Sites:

  • Run dedicated mobile crawls to test your configuration
  • Use the Fetch & Render tool set to use a smartphone user agent, the mobile-friendly testing tool and the AMP testing tool to see which content Google will use for mobile-first indexing
  • Test your robots.txt file to make sure your mobile site is accessible to Googlebot Smartphone in the first place
  • Run UX spot checks for any display or UX issues with your mobile site using an actual phone

Our mobile-first indexing PDF goes into much more detail on the topic of mobile-first indexing, including quotes from Google and industry experts. Be sure to give it a read and make sure you understand everything you need to know about this update.

Read Our Mobile-first Guide in Full