The Schema Markup Validator, at validator.schema.org, is a general-purpose tool run by the Schema.org project. It extracts every structured data item from a URL or code snippet and checks it against the Schema.org vocabulary. It was launched in 2021 as the successor to Google's Structured Data Testing Tool, and it is the right tool when you care about markup correctness beyond Google's rich results.
How it differs from the Rich Results Test
The Rich Results Test answers one question: is this page eligible for a Google feature? The validator answers a different one: is this valid Schema.org? It shows every item, including types Google ignores, and flags unknown properties, wrong value types and syntax problems. It does not check Google's required properties.
Running both is normal. The validator catches structural mistakes and stray markup from plugins. The Rich Results Test confirms Google eligibility.
Reading the output
Results show a tree of each detected item and its properties, which makes nesting problems easy to spot. If an author appears as a separate top-level item instead of inside the Article, or two Organization items appear where you expected one, the tree view shows it immediately.
Example
Finding plugin noise
A marketing team at Pellucid Forge pastes its homepage URL into the validator and finds five top-level items: its own Organization and WebSite blocks, plus a LocalBusiness from an SEO plugin, a Product from a reviews widget and a second Organization with an old logo. Cleaning up leaves two consistent, connected items.
Common mistakes
Treating it as a Google eligibility check
Passing the validator does not mean a page meets Google's requirements for a rich result. Use the Rich Results Test for that.
Ignoring warnings about unknown properties
An unrecognized property usually means a typo or an invented term. Parsers ignore it, so the data you meant to provide is lost.
Questions
Google deprecated it and moved the general validation function to validator.schema.org in 2021. Google-specific checks live in the Rich Results Test.
