Schema markup & JSON-LD: what it is and how to check it

What is schema markup?

Schema markup is structured information added to a webpage to describe entities and their properties in a machine-readable way. Schema.org provides a shared vocabulary for types such as Organization, Product, Article, Event, Person and BreadcrumbList.

What is JSON-LD?

JSON-LD is a JSON-based linked-data format and is a common way to publish Schema.org structured data in HTML. A page can contain one JSON-LD object, an array of objects, multiple JSON-LD blocks or an @graph containing several related entities.

What can a schema checker verify?

A checker can identify JSON syntax errors, detect Schema.org types, inspect nested entities and highlight properties that are absent or empty. The Notinexa Schema Checker focuses on JSON-LD present in the server-returned HTML.

Does missing a property make schema invalid?

Not necessarily. Schema.org is flexible and different consumers can have different requirements. Notinexa labels selected properties as common observations rather than automatically declaring an entity invalid when one is missing.

Schema.org validation vs Google rich results

Schema.org markup and Google's rich-result eligibility are related but not identical. Search engines support selected structured-data features and apply their own requirements. A technically well-formed JSON-LD block therefore does not guarantee a particular search result.

Why might JavaScript-generated schema be missing?

Some websites inject structured data only after client-side JavaScript runs. A server-side HTML checker does not execute that JavaScript, so such markup may not be visible in the fetched source.