Mobile-first indexing means Google uses the mobile version of your website, as seen by its smartphone crawler, to decide what your pages contain and how they rank, including for people searching on a desktop. If something is missing from the mobile version, Google treats it as missing altogether.
How mobile-first indexing works
Google crawls the web with Googlebot in two forms, one identifying as a smartphone and one as a desktop. For years the desktop version decided what was indexed. Google announced the change in 2016, began moving sites in 2018 and made it the default for new sites in 2019. Since July 2024 Google has said it indexes sites with the smartphone crawler only, so a site that does not work on a phone can drop out of the index.
In practice, Google reads the page a phone would receive: its text, headings, links, images, structured data, titles and meta tags. With responsive design, mobile and desktop share the same HTML, so there is little to go wrong. Problems appear when the mobile experience is a different build, a separate m-dot site, or a stripped-back template that hides or drops content to save space.
Content inside tabs, accordions or “show more” panels is fine, as long as it is in the HTML when the page loads. Content that only loads after a tap, or that relies on scroll events Googlebot does not trigger, or is left out of the mobile template entirely, may never be seen.
Why it matters
Many people search for local services on their phones, so Google’s choice reflects how a lot of your customers already find you. The risk is for sites built before responsive design became standard, or themes that trim the mobile layout. I regularly see mobile templates that drop the service area list, customer reviews, internal links in the sidebar, or the schema markup that the desktop version carries. Each of those is lost to Google too.
It also changes how you should judge the site. If you review your website on a laptop, you are looking at a version Google does not primarily use. Sign-off on a redesign should include walking through the main pages on an actual phone, not just a narrowed browser window.
Common mistakes
- Hiding content on mobile to keep it tidy. Removing text or sections from the mobile template removes them from Google’s view.
- Different structured data or meta tags on mobile. Titles, descriptions, canonicals and robots directives should match across versions.
- Lazy loading that waits for user interaction. Lazy loading is fine with native loading="lazy" or IntersectionObserver; content that appears only after a tap or a scroll event may be missed.
- Blocking resources for the smartphone crawler. If robots.txt blocks CSS or JavaScript, Google cannot render the mobile page properly.
- Intrusive pop-ups on mobile. Full-screen interstitials that cover the content on arrival harm the experience Google is assessing.
How to act on it
Check that your site uses responsive design; if it runs a separate mobile site, plan a move to a single responsive build. Then compare key pages on a phone and a desktop, side by side: the main text, headings, images with alt text, internal links, reviews and calls to action should all be present on both.
Use URL Inspection in Search Console to see the page as the smartphone crawler rendered it, and check the crawled HTML for anything missing. Crawl the site with a mobile user agent to compare at scale. Fixing parity problems between mobile and desktop is part of the crawl and rendering work in my technical SEO service.