Structured Data Markup Validation and Testing Tools
Tools for testing structured data markup and rich snippet display, including microformats and schema.org marked up in microdata, RDFa, RDFa Lite and JSON-LD.
When testing vocabularies and schemas, note that error messages from validators may be related to the usage requirements of only that specific data consumer, especially validation error pertaining to required fields or required properties.
Google Structured Data Testing Tool
Google Webmaster Tools
Google's tool for validating schema.org, microformats and other structured data, and for generating previews of rich snippets in Google search results for supported types. Handles HTML marked up with microdata, RDFa and RDFa Lite.
One-click access to Structured Data Testing Tool information on the page you're viewing.
Yandex Structured Data Testing Tool
Yandex's tool for validating schema.org, microformats, JSON-LD and other structured data.
Email Markup Tester
Google Developers/Google Webmaster Tools
Validator for JSON-LD and microdata, providing properties for each entity and specific error messages for invalid input.