What is Schema.org?

When your store theme, an app or an agency tells you that "schema is missing," they mean Schema.org: the list of words most of the structured data that Google reads is written with.⁠^{[1]Google Search Central. Introduction to structured data markup in Google Search} It is a website and it is a vocabulary. It is not a plugin, not a code format and not a Google tool, even though Google is one of its founders. It matters to you because it is what makes "product," "price" and "brand" mean exactly the same thing to your store, to Google and to any other program that reads your product pages.

How it works

Schema.org describes itself as a collaborative, community activity whose mission is to create, maintain and promote schemas for structured data on the internet, on web pages, in email messages and beyond. Google, Microsoft, Yahoo and Yandex founded it.⁠^{[2]Schema.org. Schema.org} Since April 2015, the project's main forum has been the W3C Schema.org Community Group, which prepares the releases, and a steering group with representatives of those search engines approves and publishes them.⁠^{[3]Schema.org. About Schema.org}

The vocabulary is organized into types and properties, in a hierarchy that starts at Thing and branches into creative works, events, organizations, people, places and products. Release V30.1, from September 16, 2026, has 826 types, 1,540 properties, 19 data types, 96 enumerations and 544 enumeration values.⁠^{[4]Schema.org. Organization of Schemas}

A type is a class of thing. Product, for example, is "any offered product or service," and Schema.org gives as examples a pair of shoes, a concert ticket, a car rental and a haircut. It hangs directly from Thing and has properties such as name, description, sku, gtin, brand, image and offers.⁠^{[5]Schema.org. Product} A property can point to another type: offers leads to Offer, which describes the terms of sale. And an enumeration is a closed list of values, like the availability ones: Google asks you to write them as vocabulary addresses, such as https://schema.org/InStock.⁠^{[6]Google Search Central. Merchant listing (Product, Offer) structured data}

Two areas of the vocabulary are worth knowing. The pending section is the testing ground for new terms that are still under discussion, and Schema.org warns that they may lack consensus and that their name or definition may change a lot. The attic keeps terms that were retired or rejected, and using them is discouraged.⁠^{[4]Schema.org. Organization of Schemas}

Schema.org does not impose a format. The same vocabulary can be written with RDFa, microdata or JSON-LD, and according to the project itself, in 2024 more than 45 million domains marked up their pages with more than 450 billion Schema.org objects.⁠^{[2]Schema.org. Schema.org}

In a store

To see what Schema.org does and does not do, follow a single piece of data, the price on a product page, through the three layers involved. Fictional example: the product and the price are made up.

Schema.org is only the first layer; the format and the requirements are decided elsewhere. The practical value of separating them is knowing whom to ask: if you doubt what a property means, read Schema.org; if you doubt whether Google takes it into account, read Google's documentation. Google puts it this way: most of the structured data its search engine uses relies on the Schema.org vocabulary, but for how Search behaves, the definitive reference is its own documentation, not Schema.org's.⁠^{[1]Google Search Central. Introduction to structured data markup in Google Search}

And inside the vocabulary, be precise. Google asks you to use the most specific type and properties Schema.org defines for what you mark up.⁠^{[8]Google Search Central. General structured data guidelines} Under Product, for example, Schema.org lists more specific types such as ProductGroup, ProductModel and IndividualProduct.⁠^{[5]Schema.org. Product}

How to check it

1. Open the type's page on Schema.org, for example schema.org/Product. You will see what it hangs from, its properties and the more specific types, and at the bottom, the vocabulary release.⁠^{[5]Schema.org. Product}
2. Look up each property in your markup on that page. If it does not appear, or appears in the pending section or the attic, do not treat it as stable.⁠^{[4]Schema.org. Organization of Schemas}
3. Run your code through a schema validator to see whether it respects the vocabulary, and then through the Rich Results Test to see what Google understands from it.
4. Open Google's documentation for the result you want (for a store, the merchant listing one) and note which properties it asks for as required and which as recommended.⁠^{[6]Google Search Central. Merchant listing (Product, Offer) structured data}

Related concept: JSON-LD

Schema.org is the words; JSON-LD is one of the ways to write them on the page. The same product page described with the same vocabulary can be written in JSON-LD, microdata or RDFa.⁠^{[2]Schema.org. Schema.org} Google supports all three and recommends JSON-LD.⁠^{[1]Google Search Central. Introduction to structured data markup in Google Search} That is why "we have schema" and "we have JSON-LD" are not the same sentence: the first is about what is said and the second about how it is written. And schema markup, the phrase you will hear in proposals, is markup made with this vocabulary, without saying in which format.

To keep going, the structured data reading path puts the rest of the terms in order, and the JSON-LD page explains the format Google recommends.