How can you check if your site has switched to Mobile-First Indexing?

What is Mobile-First Indexing and why is this verification crucial?

Mobile-First Indexing (MFI) means that Google uses the mobile version of a page for indexing and ranking, rather than the desktop version as was historically done. This shift has gradually become widespread, site by site, depending on the maturity of each web property.

Knowing if your site has switched to MFI is not trivial. If Google crawls your site as Googlebot Smartphone, any difference in content, structure, or markup between mobile and desktop directly affects your rankings. An element present only in desktop may disappear from the index. A hidden menu on mobile can hinder the crawl of deep pages.

The official verification method via Search Console provides a clear and documented response. Before this confirmation, many relied on server logs or indirect clues. Now, the status is explicitly displayed in the Coverage tab of each property.

Where can you find this information in the Search Console?

Go to the Coverage section (sometimes translated as Indexation depending on the interface versions). Select a specific page or check the reports of your indexed URLs. The Main Crawler field indicates which agent was used for the primary indexing.

If the displayed value is Smartphone, your page is indeed indexed in Mobile-First. If it shows Desktop, your site has not yet migrated. This distinction is binary and unambiguous: Google does not make compromises on this point.

This data is also visible in the URL inspection tool of the Search Console. Inspect an individual page, check the technical section, and the type of crawler is clearly stated there. This is the most reliable approach for a precise diagnosis.

Is this verification enough to guarantee good mobile indexing?

No. Knowing that Google crawls in Smartphone mode is a first step, not a quality guarantee. The transition to MFI does not automatically fix the shortcomings of your mobile version.

If your mobile content is truncated, if your images lack alt attributes or schema markup, if your mobile Core Web Vitals are disastrous, MFI will simply index a deficient version. Google's declaration relates to diagnosis, not optimization.

• The Main Crawler in Smartphone mode confirms the shift to MFI
• This information is directly accessible in the Search Console, Coverage section
• The MFI migration does not guarantee the quality of mobile indexing
• It is necessary to compare mobile and desktop to detect gaps in content, markup, and performance
• Server logs remain useful to refine the crawl diagnosis

Is this statement consistent with observed practices on the ground?

Yes, perfectly. SEO teams who regularly monitor the Search Console quickly spotted this data in the interfaces. It is reliable and corresponds to observations made in the server logs: when the Main Crawler switches to Smartphone, the dominant requests indeed come from the mobile Googlebot.

However, Google remains vague about the exact migration timeline for each site. Some sectors have switched more quickly than others, without any clear logic emerging. The statement also does not specify the criteria that trigger or delay migration. [To be verified]: No public indicator allows us to predict when a site will be migrated.

What nuances should be added to this verification?

The status of the Main Crawler says nothing about crawl frequency, nor about the actual coverage rate of your pages. A page can be indexed in Smartphone mode but crawled very rarely, especially if it is deep or if your crawl budget is limited.

Moreover, Google may occasionally crawl in Desktop mode even after MFI migration, particularly for ad hoc checks or for certain types of content. The Main Crawler reflects the primary agent, but it is not the only asset on your site. Monitor your logs for a comprehensive view.

Another point: this verification assumes that you have properly validated your mobile property in the Search Console. If you have only configured the desktop version or if your site is responsive, ensure that the declared property corresponds correctly to what Google is indexing.

In what cases does this rule not apply or does it pose a problem?

If you have a separate desktop site and a mobile site on a subdomain or a distinct path (m.mysite.com, mysite.com/m/), the verification must be done on the correct property. Confusing the two can skew the diagnosis. Make sure you are consulting the property that Google is prioritizing for indexing.

For AMP sites, the situation can be more complex. Google sometimes indexes the AMP version, sometimes the canonical version. The Main Crawler may indicate Smartphone, but the URL served in the SERPs may be the AMP. This distinction does not change the MFI itself but complicates tracking the version actually indexed.

What should you do concretely to verify and utilize this information?

Log into the Search Console and navigate to the Coverage section (or Indexation depending on your interface). Select a representative sample of strategic pages — category pages, product listings, pillar articles — and inspect the Main Crawler field for each.

If you find that some pages are still crawled in Desktop mode, identify the common factors. Are they recent pages? Pages with few inbound links? Pages on a specific subdomain? This segmentation will help you understand the migration logic applied by Google to your site.

At the same time, download your server logs over a period of at least 30 days and analyze the distribution of user-agents Googlebot Desktop vs Smartphone. Cross-reference this data with that from the Search Console to detect possible inconsistencies or overlooked pages.

What mistakes to avoid after confirming the transition to MFI?

Never assume that mobile and desktop are equivalent without verifying manually. Crawl your site using a mobile user-agent with Screaming Frog or Oncrawl, then compare the results with a Desktop crawl. Look for discrepancies in content, internal linking, Hn tags, and schema markup.

Also, avoid neglecting mobile performance on the pretext that indexing is secured. Core Web Vitals impact ranking, and a slow mobile site will be penalized even if it is well indexed. Test your pages on actual mobile devices, not just on a desktop emulator.

Finally, do not modify your mobile version without testing the impact on indexing. Any change to templates, accordions, lazy-loading, or scripts can affect what Google sees and indexes. Establish strict monitoring of positions and impressions after each deployment.

How can you verify that your mobile implementation is truly compliant?

Use the URL inspection tool of the Search Console to visualize the version rendered by Google. Compare the rendered HTML to the source HTML, especially for JavaScript. If content only appears client-side post-JS execution, ensure that Googlebot can see it.

Verify that your structured data is present in the mobile version and identical to that of desktop. Test with the rich results testing tool. If you have schema for Product, Article, or FAQ, it must be visible and valid on mobile.

Also, check that your images have proper alt attributes, suitable srcset tags, and that lazy-loading does not prevent the indexing of strategic visuals. Google Image Search can generate significant traffic: do not sacrifice it due to negligence.

• Check the status of the Main Crawler in the Search Console, Coverage section
• Crawl your site with a mobile user-agent and compare it with a Desktop crawl
• Analyze your server logs to confirm the distribution of Googlebot Desktop vs Smartphone
• Test the mobile rendering with the URL inspection tool from the Search Console
• Validate the presence and compliance of your structured data in the mobile version
• Monitor your mobile Core Web Vitals and resolve friction points