Glossaire · SEO

Structured data

Structured data refers to a standardized markup format, based on the Schema.org vocabulary, that explicitly describes the meaning of a web page to search engines and AI models. Instead of letting a machine guess that content is a recipe, a product or a review, structured data labels each piece of information (price, rating, author, date) in a language that algorithms and LLMs understand without ambiguity. On the web, the format Google recommends is JSON-LD, a block of code inserted into the page's HTML. This data powers rich snippets, the Knowledge Graph, AI Overviews and the answers given by conversational assistants. It does not change what the visitor sees on the page: it provides a parallel semantic layer, readable by machines, that improves understanding, eligibility for enhanced displays and citability within AI-generated answers in 2026.

Structured data has become one of the most cost-effective SEO levers of 2026, because it speaks the language of machines directly, whether that is Googlebot or the models that generate AI answers.

How it works

A standard web page is a stream of text and HTML tags designed for the human eye. A machine, however, has to guess the nature of each element. Structured data removes that ambiguity by mapping each piece of information to a type defined by Schema.org: Product, Article, Recipe, FAQPage, LocalBusiness, and so on.

In practice, you insert a JSON-LD script into the page's <head> or <body>:

the entity type being described (@type),
its properties (name, price, rating, author),
its relationships with other entities.

Google reads this block during the crawl, validates it, then uses it to enrich the SERP display or feed its AI systems.

Why it matters

Three benefits compound. First, eligibility for rich snippets: review stars, prices, expandable FAQs, breadcrumbs. These displays lift click-through rate without gaining ranking. Second, entity disambiguation, which strengthens your presence in the Knowledge Graph. Finally, and this is new, LLMs rely on this data to understand and cite a page: well-marked-up content is more easily extracted and attributed within a generated answer.

Key takeaway

Structured data changes nothing the visitor sees, but it transforms what Google and AI understand. It is an invisible layer with high returns.

A concrete example

A product page displays "4.8 stars, 230 reviews, €49". Without markup, Google sees text. With a Product + AggregateRating + Offer schema, this data surfaces directly in the SERP as stars and price, and stays available to an AI assistant queried about the product. The data already existed; markup makes it usable by machines.

FAQ

Questions fréquentes

Google recommends JSON-LD, a code block injected into the HTML, over microdata or RDFa. It is the easiest format to maintain and the least likely to break during site updates.

No. Valid markup makes your page eligible for rich results, but Google alone decides whether to display them based on page quality and the query. Markup is a necessary but not sufficient condition.

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