In more detail
For many years, Google crawled and indexed the desktop version of pages. As most searches moved to phones, Google switched to crawling primarily with a smartphone user agent. Its mobile-first indexing best practices explain what this means for site owners.
On a responsive website, where the same HTML adapts to screen size, there's usually little to do. Problems arise when the mobile experience differs from desktop:
- Content, reviews or specifications hidden or removed on mobile to save space
- Fewer internal links in mobile navigation
- Images lazy-loaded in ways crawlers can't trigger, or missing alt text on mobile
- Structured data or metadata present only on the desktop version
- Separate mobile URLs (such as m.example.com) that aren't correctly connected to desktop pages
Google's guidance is to make sure the mobile site has the same content as the desktop site, the same structured data and metadata, and that it allows Googlebot to crawl its resources.
Content in tabs or accordions on mobile can still be indexed, as long as it's present in the HTML.
Why it matters when hiring an agency
Mobile parity should be part of every technical audit. Ask an agency how it checks: good practice includes crawling the site as a smartphone and comparing the content with the desktop version, not just looking at a phone screen.
If you're planning a redesign, ask your agency to review mobile templates before launch. A mobile design that trims content to look clean can quietly remove the text and links that pages rank with.