GlossarySEO
What is structured data (JSON-LD)?
Also called: schema markup, schema.org, JSON-LD
Definition
Structured data is machine-readable information about a page, usually written as JSON-LD using the schema.org vocabulary. It helps search engines understand what a page is about and can make it eligible for rich results.
Structured data (JSON-LD), explained
Google describes structured data as a standardized format for providing information about a page and classifying its content. A product page can state its name, price and rating; an article can state its headline, author and dates; a breadcrumb trail can state where the page sits in your site. Search engines can read all of that from the HTML, but structured data states it explicitly.
There are three formats Google supports: JSON-LD, Microdata and RDFa. Google recommends JSON-LD where your setup allows, because it lives in its own <script type="application/ld+json"> block instead of being woven into your visible HTML, which makes it easier to add and maintain at scale. The vocabulary almost everyone uses is schema.org.
The main visible payoff in Google is rich results: breadcrumbs, product details, review stars, event dates and so on. But structured data doesn't guarantee any of them. You need the required properties for the feature, the markup has to match what's visible on the page, and Google decides whether to show it. Google also retires features over time; FAQ rich results, for example, stopped appearing in 2026.
Useful types for most startup sites: Organization on the homepage, WebSite, BreadcrumbList on inner pages, Article on blog posts, SoftwareApplication or Product for what you sell, and DefinedTerm for glossary pages like this one. Keep it accurate. Marking up content people can't see, or reviews you didn't collect, breaks Google's structured data guidelines.
Test with Google's Rich Results Test or the Schema Markup Validator, and watch the enhancement reports in Search Console for errors after deploys.
Why it matters for founders
Structured data is cheap to add once in a shared helper and then applies to every page. It makes your pages clearer to search engines and eligible for richer results, which can mean more clicks at the same position.
Example
Each page on this glossary includes a DefinedTerm JSON-LD block with the term's name, definition and URL, plus a BreadcrumbList showing Home › Glossary › the term.
Common mistakes
- Marking up content that isn't visible on the page.
- Expecting rich results just because the markup validates.
- Hand-writing JSON-LD per page instead of generating it from one helper.
- Leaving markup for retired features and assuming it still shows.
Sources
Checked
Related terms
- FAQ schemaFAQ schema is FAQPage structured data that marks up a list of questions and answers on a page. Google no longer shows FAQ rich results in Search, but the markup remains valid schema.org.
- Featured snippetA featured snippet is a Google result where the descriptive snippet appears first, above the link, to answer a query directly. Google picks it automatically; there's no markup that makes a page one.
- SERPA SERP (search engine results page) is the page a search engine shows after a query: the list of links plus features like AI Overviews, featured snippets, videos, ads and "People also ask" boxes.
- E-E-A-TE-E-A-T stands for experience, expertise, authoritativeness and trustworthiness. It's the framework Google's quality raters use to judge content. It isn't a single ranking factor, but Google's systems look for signals of it.