JSON Schema is a declarative language for validating JSON documents' structure, constraints, and data types. It provides a way to standardize and define expectations for JSON data.
JSON Schema is adopted by several reputed orgs. to validate the JSON Data in their internals some of them include Github, Microsoft, Zapier, Schema Store, Postman, etc... a landscape of all orgs. using them can be found here.
JSON Schema website which is the website from where users can learn more about JSON Schema specifications, documentation, tools, community, and blogs written by JSON Schema developers.