Is mobile-first indexing truly the top priority for your SEO?

What exactly is mobile-first indexing?

Mobile-first indexing does not mean that Google completely ignores the desktop version. It simply prefers the mobile version for crawling, indexing, and ranking. In other words, it is the content of your mobile page that Googlebot analyzes first to determine your relevance for a query.

This statement from Kristina Azarenko confirms what has been evident for years: the mobile version has become the reference. If your mobile version is incomplete, limited, or different from the desktop, you lose positions. It's as simple as that.

How long has this practice been widespread?

Google began gradually rolling out mobile-first indexing in 2018 and fully implemented it for all sites in 2021. Therefore, it is no longer a novelty, but an operational reality that should have been integrated into all SEO audits for a long time.

Yet, many sites continue to display truncated content on mobile due to concerns about UX or design. The result: Google indexes less content, and the site loses visibility on crucial queries.

Why was this change implemented?

The answer is obvious: the majority of searches are done on mobile. Google follows user behavior. Indexing primarily the desktop version no longer made sense when 60 to 70% of queries come from smartphones.

This shift forces webmasters to rethink their approach: it is no longer about adapting a desktop site to mobile, but rather about designing for mobile first and then potentially enhancing the desktop version.

• Mobile-first means that Googlebot primarily crawls and indexes the mobile version of your pages
• The desktop version is no longer the reference for ranking in search results
• Content that is absent or different on mobile will be ignored by Google, even if it is present on desktop
• The Core Web Vitals and mobile performance are becoming even more crucial ranking criteria
• Sites that have not yet migrated to a responsive design or equivalent mobile version risk significant declines in organic traffic

Is this statement really a novelty?

Let’s be honest: no, absolutely not. Google has been communicating about mobile-first indexing since 2016, began gradually rolling it out in 2018, and fully implemented it in 2021. This statement from Kristina Azarenko is a reminder, not a revelation.

What’s interesting is that she insists on it — which suggests that many sites are still not compliant. And that’s probably true: we still regularly see sites with hidden content on mobile, lazy-loaded images without correct attributes, or structured data missing from the mobile version.

What nuances should we add to this claim?

Google says “primarily” mobile-first, not “exclusively.” In some cases, particularly for desktop-only sites (yes, they still exist), Google may index the desktop version. But this is an exception, not the rule. [To verify]: Google has never published precise data on the percentage of sites still indexed in desktop-first mode.

Another crucial point: mobile-first does not mean mobile-only. Your desktop version still matters for user experience, conversions, and some indirect signals (session duration, bounce rate). But for crawling and indexing, it is indeed the mobile version that takes precedence.

In what cases does this rule still pose a problem?

The sites that suffer the most are those that have historically displayed different content between mobile and desktop. Typically: text hidden behind accordions that are not expanded by default, improperly configured lazy-loading images, or hidden menus that prevent Googlebot from discovering certain pages.

Another problematic case: e-commerce sites that hide complete product descriptions on mobile to “lighten” the interface. The result: Google indexes product sheets that are poor in content, and the site loses positions against competitors who display everything on mobile.

What should you prioritize checking on your site?

First step: audi the strict equivalence between mobile and desktop. Open a tab in mobile mode (Chrome DevTools, smartphone viewport) and compare line by line with the desktop version. Is the textual content identical? Are the <title>, <meta description>, <h1>, <h2> tags rigorously the same?

Second point: check that Googlebot mobile can crawl all your strategic pages. Use Google Search Console, URL Inspection section, and force the crawl in mobile mode. Look at the HTML rendering: is all the content visible?

What mistakes should you absolutely avoid?

Never hide important SEO content on mobile under the pretext of UX. If your design team wants to hide text in an accordion, ensure that it is expanded by default or at least visible in the DOM without user interaction.

Avoid also robots.txt files that block critical CSS or JS resources on mobile. Google needs these resources to understand the layout and index correctly. A poorly configured block can prevent the indexing of entire sections of your site.

How can I ensure my site is compliant?

Use Google’s mobile optimization testing tool, but don’t stop there. Run a crawl using Screaming Frog or Oncrawl in mobile user-agent mode, and compare the results with a desktop crawl. You should see the same URLs, the same number of words per page, and the same tags.

Finally, monitor your Core Web Vitals on mobile in Search Console. Mobile-first indexing is not limited to content: performance also matters. A 4-second LCP on mobile penalizes you, even if your desktop is fast.

• Compare line by line the mobile and desktop content to detect differences
• Check that all meta tags, titles, and structured data are identical on mobile
• Test the mobile rendering via the URL Inspection tool in Search Console
• Crawl the site in mobile user-agent and compare with a desktop crawl
• Remove display:none from strategic SEO content in mobile version
• Optimize Core Web Vitals specifically on mobile (LCP, CLS, FID)