What Is Structured Data?

How Structured Data Works

Plain HTML tells a browser how to display content — this is a heading, that is a paragraph — but it says nothing about what the content means. A search engine reading <span>4.8</span> has no built-in way to know whether that number is a star rating, a product version, or a price. Structured data closes that gap by attaching an explicit, standardized label to each piece of information: this value is an aggregateRating, that value is a priceCurrency, this date is an eventStartDate.

Google’s own documentation frames it plainly: structured data provides “explicit clues about the meaning of a page” and is “a standardized format for providing information about a page and classifying the page content.” Once an engine can classify content with confidence, it can do two things it otherwise couldn’t. First, it understands the page’s entities well enough to place them in its knowledge of the web. Second, it can present the page as a rich result — a listing enhanced with stars, images, prices, or expandable questions instead of a plain blue link.

Nearly all structured data for search uses the schema.org vocabulary — a shared library of types (Product, Recipe, Article, Event) and properties that the major search engines all recognize. The vocabulary supplies the words; the format supplies the grammar for placing them on the page.

The Three Formats

Google Search reads structured data in three interchangeable syntaxes, and its documentation states that “all 3 formats are equally fine for Google, as long as the markup is valid and properly implemented”:

• JSON-LD — a block of JavaScript notation inside a <script type="application/ld+json"> tag, kept separate from the visible HTML. Google recommends it as “the easiest solution for website owners to implement and maintain at scale.”
• Microdata — HTML attributes (itemscope, itemprop, itemtype) woven directly into the visible markup of the page.
• RDFa — an HTML5 extension that, like Microdata, annotates existing visible elements with attributes.

The practical trade-off is maintenance. Because JSON-LD lives in one detached block, it doesn’t break when a designer restructures the page’s HTML, which is why it has become the default for SEO work.

Example of Structured Data

The clearest documented example is Google’s own structured data program, described in its Search Central documentation. Google publishes a search gallery of the specific features that structured data can unlock, and as of 2026 that gallery documents 31 distinct structured data features — among them Article, Breadcrumb, Product, Review snippet, Recipe, Event, FAQ-style Q&A, Video, Job posting, and Local business.

Each feature has a documented contract. A Product marked up with a valid offers block and an aggregateRating, for instance, becomes eligible for a merchant listing that can show price and star ratings directly in results. Google’s documentation is explicit that eligibility is conditional: the required properties must be present, the markup must be valid, and — critically — the information must be “visible to the user” on the page. Mark up a rating the reader can’t see, and the page can lose eligibility under Google’s structured data guidelines rather than gain a feature.

What makes this a useful worked example rather than folklore is that the mechanism is fully documented and testable. You can take any page, run it through Google’s Rich Results Test, and get back exactly which of the 31 features the page qualifies for and which required properties are missing — a deterministic check, not a guess. The lesson generalizes: structured data is a contract with the search engine. You supply valid, visible, correctly-typed information; the engine grants eligibility for a specific enhanced appearance. Nothing about that contract promises a higher rank — it promises comprehension and a shot at a better-looking listing.

Structured Data vs Schema Markup

The two terms are used almost interchangeably in day-to-day SEO, and for good reason: when an SEO says “add structured data,” they nearly always mean schema.org markup written in JSON-LD. The distinction only matters when precision does — structured data is the wider category, and schema markup is the specific vocabulary that dominates search use of it.

Frequently Asked Questions

The Bottom Line

Structured data is the labeling layer that turns human-readable text into something a search engine can parse without guessing. It does not push a page up the rankings by itself; it removes ambiguity about what the content means and unlocks the possibility of a richer, more clickable listing. Get the format valid, keep it faithful to what’s on the page, and you give the engine every reason to display your result at its best.