Structured data (JSON-LD)

Machine-readable annotations that describe the content of a page using the schema.org vocabulary. JSON-LD is the format search engines and AI agents expect.

What it is

Structured data is a set of machine-readable statements that describe what a page is about, using the shared vocabulary at schema.org. The recommended serialisation is JSON-LD: a <script type="application/ld+json"> block inside <head> (or, less commonly, <body>).

<script type="application/ld+json">
{
  "@context": "https://schema.org",
  "@type": "Article",
  "headline": "What is HSTS?",
  "datePublished": "2026-05-29",
  "author": {
    "@type": "Person",
    "name": "Jane Doe"
  },
  "publisher": {
    "@type": "Organization",
    "name": "Example",
    "url": "https://example.com"
  }
}
</script>

Microdata and RDFa are also accepted, but JSON-LD is the de facto standard because it sits separate from the visible markup.

Why it matters

Two audiences read it heavily:

Search engines use structured data to power rich results (article cards, breadcrumbs, FAQ accordions, product carousels, knowledge-panel facts). Without it, you get a plain blue link.
AI agents and answer engines rely on it as the ground truth for facts they may quote. A Person schema with a sameAs linking to your verified profiles is the cleanest way to assert identity.

It is also the most stable contract between a publisher and the rest of the web. The HTML can change; the JSON-LD describes meaning.

How to implement

Stick to a small set of well-supported types:

WebSite — site-wide, on the home page. Include url and name, and potentialAction for sitelinks search if appropriate.
Organization or Person — for the publisher and authors. Include sameAs arrays pointing at verified profiles.
BreadcrumbList — on every page that has a breadcrumb trail.
Article or BlogPosting — for articles, with headline, datePublished, dateModified, author, image.
Product, Offer, AggregateRating — for e-commerce, where eligibility is strict.
FAQPage — only when the page genuinely has a Q-and-A list visible to users. Google has restricted FAQ rich results to authoritative publishers; do not stuff fake FAQs.

Rules:

Mirror what is visible on the page. Do not declare facts in JSON-LD that the page does not state. Google calls this "out of sync" data and ignores or penalises it.
One graph per page is cleaner than many fragments. Use @graph to nest related entities and @id URIs to cross-reference them.
Use absolute URLs in @id, url, image, and sameAs.
Keep dates in ISO 8601.
Validate. Schema.org evolves; what is valid one year may be deprecated the next.

Common mistakes

Fabricating aggregateRating or Review to win stars. Google detects this and removes the rich result, sometimes the whole site's eligibility.
Marking up navigation, footers, or sidebars as if they were the main content.
Forgetting to update structured data when the page content changes.
Multiple disagreeing @type declarations across plugins or templates on the same page.

Verification

Use the Schema.org validator for spec conformance.
Use Google's Rich Results Test for eligibility.
Check Search Console's "Enhancements" reports after deployment.