Yup

Yup is a schema builder for runtime value parsing and validation, now at v1.7.1 with active development. It provides a concise, chainable API for defining schemas that can parse, coerce, and validate complex nested objects, with built-in async support and rich error details. Key differentiators include powerful TypeScript inference via InferType, seamless integration with Standard Schema, and extensibility through custom methods. It remains a top choice for form validation in React ecosystems (Formik) and general data validation, competing with Zod (more lightweight) and Joi (Node-only).