Typanion

Typanion is a lean, type-safe runtime TypeScript validator library with zero external runtime dependencies. It excels at validating complex, nested data structures and provides strong type inference, which allows TypeScript to refine types based on successful validation. Unlike some alternatives, Typanion emphasizes a functional and tree-shakeable API, making it efficient for bundlers. It provides detailed error reports and supports coercions, enabling data transformation during validation. While it may not have the extensive ecosystem of libraries like Zod or Yup, its core differentiators lie in its minimal footprint, functional design, and robust TypeScript inference. Currently, in version 3.14.0, its release cadence appears less frequent, suggesting a focus on stability over rapid iteration, with the last major activity around two years ago.