Definition
Structured data is standardised, machine-readable markup added to a web page so search engines and AI systems can understand what the page is about, not just read its words. The dominant vocabulary is Schema.org, with more than 800 types covering products, articles, businesses, reviews, FAQs, and breadcrumb trails, and the format Google recommends is JSON-LD: a small script block placed in the page that labels these entities without altering visible content. Google parses this markup to generate rich results such as star ratings, FAQ accordions, and sitelinks in search listings, while AI answer engines such as ChatGPT and Perplexity use it to extract facts more reliably than by parsing prose. Correct structured data does not directly raise rankings; it makes a page eligible for richer, more prominent listings and more citable by AI. The page still needs solid underlying content, and invalid or invented markup, such as a rating with no reviews, can trigger a manual action rather than any benefit.
How it works
A structured-data block is added to the page HTML, most often as a <script type="application/ld+json"> element containing Schema.org types and properties. Common types include Product with AggregateRating, Article, LocalBusiness, FAQPage, BreadcrumbList, and Organization. Each type has required and recommended properties; Google validates them with the Rich Results Test and reports errors in Search Console. A single page can carry several blocks describing different entities.
Why it matters
Structured data is how a page earns rich results and becomes quotable by AI answer engines. A product page with valid Product and AggregateRating markup can show star ratings in search; an FAQPage block can surface expandable questions; a well-marked-up entity is far more likely to be cited correctly by ChatGPT, Perplexity, and Google AI Overviews. Invalid or invented markup (a rating with no reviews, a price that is not on the page) is worse than none and can trigger manual actions, so the data must always match what the page actually shows.