What schema markup does
Schema markup is structured data, written in the schema.org vocabulary, that tells search engines exactly what a page is about: this is a Product with a price, this is an Article by this author, these are the questions in an FAQ. Google uses it to show rich results such as star ratings, breadcrumbs and product details, and AI answer engines read it to understand entities. It does not directly raise rankings, but it makes the result more informative, which can lift clicks.
JSON-LD, microdata and RDFa
There are three ways to add structured data. JSON-LD is a script block in the page and is what Google recommends. Microdata puts itemscope and itemtype attributes on the HTML itself. RDFa is similar and rare today. This checker parses JSON-LD in full and counts microdata types so you can see if a theme is adding old markup alongside the new.
Common problems the checker catches
- Invalid JSON. A trailing comma or an unescaped quote breaks the whole block, and search engines then ignore all of it. The error message points at the cause.
- No @context. Without
"@context": "https://schema.org", the types do not resolve. - Missing required properties. An Article without a headline, a Product without a name, an Event without a start date.
- Duplicate entities. Two Organization blocks from two plugins, often with conflicting details.
@graph and nested types
Many sites put several entities in one @graph array: WebSite, Organization, WebPage and BreadcrumbList together. The checker lists every type it finds, including nested ones like an ImageObject inside a logo, so you can see the full picture.
Passing this check is not the same as earning a rich result
Valid markup is required, but Google decides whether to show a rich result based on the page, the query and its own policies. Use Google's Rich Results Test for eligibility once the JSON is clean. To write new markup, use the schema markup generator or the FAQ schema generator.