What is Schema.org? The Vocabulary Behind All Structured Data

When you add structured data to your website, you are not just writing code — you are speaking a specific language that search engines understand. That language is defined by Schema.org. Created jointly by Google, Bing, Yahoo, and Yandex in 2011, Schema.org is the shared dictionary that defines what terms like "Product", "Recipe", "ratingValue", and "author" mean in the context of web content.

1. The Analogy: Schema.org as a Dictionary

Imagine you want to describe a book to someone who speaks a different language. You both agree in advance that the word liber means "book", auctor means "author", and paginae means "number of pages". Now you can communicate about books unambiguously.

Schema.org does exactly this for web content and search engines. It defines agreed-upon terms — called Types and Properties — so that when you write "@type": "Recipe" and "cookTime": "PT30M", every search engine that speaks Schema.org knows what you mean.

2. Types and Properties: The Two Building Blocks

3. Schema.org Type Hierarchy

All Schema.org types inherit from a root type called Thing. More specific types inherit all the properties of their parent — for example, BlogPosting inherits all properties from Article, which inherits from CreativeWork, which inherits from Thing.

4. Schema.org vs JSON-LD: What's the Difference?

5. Which Schema.org Types Does Google Support for Rich Results?

6. How to Look Up Any Schema.org Type

7. How Schema.org Evolves: Who Controls It?

Schema.org is governed by a W3C Community Group — an open collaborative group that includes Google, Microsoft, Yahoo, Yandex, and community members from academia and industry. Understanding this process helps you anticipate what is coming and why certain types exist:

8. Critical Properties You Should Know But Often Miss

Beyond the obvious type-specific properties, three Schema.org properties appear in advanced implementations across every schema type:

{
  "@context": "https://schema.org",
  "@type": "Article",
  "@id": "https://example.com/article-slug#article",
  // @id creates a globally unique identifier for this entity.
  // It anchors the entity in Google's Knowledge Graph.
  // Use a fragment URL (#article, #org, #person) to distinguish
  // multiple entities on the same page URL.

  "sameAs": [
    "https://en.wikipedia.org/wiki/Author_Name",
    "https://www.wikidata.org/wiki/Q12345",
    "https://twitter.com/authorhandle"
  ],
  // sameAs links this entity to authoritative external representations.
  // Google uses sameAs to confirm you are talking about a known
  // real-world entity, not just a name string. It is the most
  // important property for entity disambiguation.

  "mainEntityOfPage": "https://example.com/article-slug"
  // mainEntityOfPage declares that THIS page primarily exists to
  // describe this entity. Use it on your most important entities.
  // Helpful for Google to understand page-entity relationships.
}

9. Common Misconceptions About Schema.org