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Mobile-first Indexing

Mobile-first indexing was introduced in 2018 and it means that Google will consider the mobile version of a site’s content to rank pages and to understand and collect further data from a site. It is therefore very important to ensure the mobile version of your site is optimized for both users and search engine crawlers. Our SEO Office Hours notes below compile key insights relating to mobile-first indexing, from Google Search Central’s ongoing advice sessions.

For more about mobile website versions & SEO, check out our additional resources:

The Ultimate Guide to Google’s Mobile-first Index 

An SEO’s Guide to Mobile Site Speed & Performance

Sites typically won’t get punished for having different content on mobile and desktop

Because Google has switched to mobile-first indexing, this means that Google very rarely crawls the desktop version of a site. Therefore, punishment for differences between the versions is unlikely, as any differences between mobile and desktop probably won’t even be detected. Googlebot does crawl the alternate version of a site from time to time, but this is primarily to confirm the connection between the two, rather than to compare the content.


17 Mar 2022

Google Will Only Use Content From Mobile Pages if Mobile First

Google will only use the mobile version of content when a site has been moved to mobile first. If your mobile pages have less structured data or images than your desktop pages, Google will not use the content from your desktop site. Google will continue to crawl your desktop pages about 20% of the time to make sure they are not missing any new pages.

6 Mar 2020

Google Recommends a Single Site for Mobile First Indexing

It’s OK to have a separate mobile website for mobile first indexing, provided it’s correctly linked from the desktop version with a mobile rel alternate and a canonical pointing to the desktop page, but Google recommends having a single URL for each piece of content with responsive design or dynamic serving in the future.

6 Mar 2020

Google Determines Mobile Usability Based on The Ability to Render the Page

Google determines mobile usability results based on the ability to render pages in a way that matches what a user would see on their device. Sometimes they may face issues when fetching the CSS or JavaScript files and this will display a small number of issues, with regards to mobile usability, in Google Search Console. However, John advised these are usually based on temporary fluctuations in Google’s ability to fetch individual files, but it will not affect the indexing of these pages.

26 Nov 2019

Google May Still Crawl Parts of a Site With Desktop Crawler

Even with the shift to mobile-first indexing, Google may still crawl parts of a site with the desktop crawler. John explained that this will not impact the site as long as things are working well on mobile.

15 Nov 2019

Canonical Tags Should Remain The Same Between Desktop & Mobile Sites Even With Mobile First Indexing

If you have a separate m. version of your site, the canonical should remain pointing to the desktop version, despite mobile-first indexing. This is because Google will use the canonical tag to understand which of the pages belong together. Internally, Google will pick the mobile version as canonical.

18 Oct 2019

Google Uses the Viewport Tag to Understand the Mobile-friendliness of a Page

The viewport tag is used for scaling a page for devices, and Google will use this tag to understand whether the page is mobile-friendly or not. Google won’t automatically categorise a page as a mobile version if it has a viewport tag.

4 Oct 2019

Mobile-first Readiness Classifer Will Review Content On Both Mobile & Desktop Sites

With mobile-first indexing, Google will only index what it is able to crawl on the mobile version of the site, so if there is important content on the desktop version which is not available on the mobile version, this will not be indexed. The readiness classifier will be used to recognise if the content is similar enough on both, before switching to mobile-first indexing.

6 Sep 2019

A Readiness Classifier & Algorithm is Used to Determine Mobile-first IndexingA Readiness Classifier & Algorithm is Used to Determine Mobile-first Indexing

A readiness classifier is used to determine whether or not pages are ready for mobile-first indexing and looks at elements like internal linking, anchor text and content differences. However, if the algorithm determines that the majority of pages are ready then the site will be moved, even if some pages have content inconsistencies. This could impact rankings.

3 Sep 2019

Mobile-first Indexing Isn’t a Ranking Factor or Quality Signal

There’s no need to push a site to be moved to mobile-first indexing. This is only a technical change in the way pages are crawled and indexed, and being in the mobile-first index doesn’t come with any quality signals or ranking boosts.

3 Sep 2019

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