Mobile-First Indexing
Mobile-first indexing means Google uses the mobile version of your pages for indexing and ranking. It has applied to all sites since 2023. If content is hidden, trimmed or absent on mobile, Google effectively does not see it at all.
Why it matters for your rankings
The consequences are frequently invisible to the people responsible. Teams review the site on a desktop, see everything intact, and never learn that the mobile template drops half the copy behind an accordion the crawler treats differently or omits it entirely.
Responsive designs mostly avoid this. Separate mobile templates and dynamic serving do not, and those are where content parity breaks silently. The same applies to structured data, internal links and metadata: if any of them exist only on the desktop version, they are functionally gone. Since mobile also carries the majority of traffic in most categories, this is simultaneously an indexing issue and a conversion issue, which makes it one of the highest-leverage checks in a technical audit.
How to check it on your site
Compare content parity
View a key page on desktop and mobile and compare the visible text, headings and links. Anything missing on mobile is missing from Google's index.
Check structured data on both
Run the mobile URL through the Rich Results Test. Schema present only on desktop will not be counted.
Test with the mobile crawler
Crawl with Screaming Frog using the Googlebot Smartphone user agent and compare word counts against a desktop crawl.
Confirm mobile usability
Check tap target spacing, font size and viewport configuration, since these affect both rankings and conversion.