Mobile-First Indexing
Mobile-first indexing is Google's practice of using the mobile version of a site's content, crawled with its smartphone crawler, to index and rank pages. Google's guide says the mobile site should hold the same content as the desktop site, because only content on the mobile version is used for indexing.
Source: Google Search Central, Mobile site and mobile-first indexing best practices, checked October 29, 2026
What Mobile-First Indexing means for your business
Google began the switch in 2016 and said in an October 2023 post that it was complete. If your site uses one design that resizes for phones, most of this takes care of itself. Trouble starts when the phone version shows less. Google says it "won't load content that requires user interactions (for example, swiping, clicking, or typing) to load," so text that only loads after a tap, rather than sitting on the page inside a tab or accordion, may be missed.
Google also asks for the same structured data, the same title and an equal meta description on both versions. If a mobile theme leaves out your reviews, FAQ answers or schema, Google doesn't see them.
The October 2023 post says a small set of sites don't work on phones at all: pages that show errors to every mobile visitor, a mobile site blocked in robots.txt, or every mobile page sending people to the home page. In that post, Google said it would keep crawling those with its older desktop crawler for the time being, and that it can't fix them for you.
We'd open your main pages on a phone and on a computer side by side and look for anything missing: the service list, hours, reviews or answers. If your phone site is a trimmed-down copy of your desktop site, making sure Google reads the full version is part of our SEO work.
Source: Google Search Central Blog, Mobile-first indexing has landed (October 31, 2023), checked October 29, 2026
Last reviewed October 29, 2026. All terms
How AI answers it today
On October 29, 2026, Google's AI Overview cited Google's own guide alongside Moz, Semrush, agency blogs and YouTube, and matched the guide's definition. ChatGPT gave a similar definition with a made-up desktop and mobile example and cited nothing.
Our run through ChatGPT and Google's AI Overview, October 29, 2026. A sample, not what every buyer sees.
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