The official validator.schema.org tool used to check structured data syntax and conformity with Schema.org standards.
The Schema.org Markup Validator examines structured data using the Schema.org vocabulary. It can fetch a page or inspect supplied markup, extract supported formats and display the resulting data graph. It helps find syntax problems and inspect the entities and relationships represented.
This is different from testing eligibility for a particular Google rich result. Schema.org includes many types and properties beyond those used by a specific search feature. A valid structure may therefore produce no special Google display, even when the tool reports no obvious syntax problem.
Validation also cannot establish that the facts are true. A well-formed business address, rating or author object can still be inaccurate or misleading. Review the markup against visible content and real evidence rather than treating a clean result as approval of the claims.
Takeaway: Use the validator as one layer of quality assurance. Follow structural checks with factual review and any separate feature-specific requirements.
Example
A service page contains a valid Service object naming its provider and area served. The validator can help inspect that representation. It does not prove the provider actually serves every listed area or that Google will show a service-specific rich result.
What to check
Test the actual published page after template changes, not only a sample snippet. Inspect duplicate or conflicting entities from plugins. Keep syntax validity, content accuracy and Google eligibility as separate review questions.
For more detail, see Schema.org Markup Validator.