JSON-LD

JSON-LD is the format Google recommends for structured data. Instead of weaving attributes through your HTML (as Microdata and RDFa do), you place one or more script blocks of type application/ld+json in the page, each a self-contained JSON object describing an entity. This separation is why it is preferred: the markup does not entangle with presentation, it is easy to generate from data, and it is straightforward to validate.

A JSON-LD block declares a context (usually schema.org) and a type (Organization, Article, Product, LocalBusiness, FAQPage, BreadcrumbList, and so on), then lists the properties. Multiple blocks can describe different entities on the same page, and the graph form can express relationships between them, for example an Article authored by a Person who works for an Organization.

The practical rules: render it server-side so non-JS crawlers see it, keep it consistent with the visible content, validate it, and avoid marking up content that is not actually present. Because it is just data, JSON-LD is easy to template, which is how we generate it across our own glossary, methodology, blog, and comparison pages without a third-party schema library.