io-ts: Runtime Type System for TypeScript

io-ts is a TypeScript library providing a robust runtime type system, designed for decoding and encoding data at the boundaries of your application. It allows developers to define types once using its codec combinators, which then serve for both static type checking during development and dynamic validation of external data at runtime. This approach significantly reduces common errors when integrating with uncertain data sources like API responses, user input, or configuration files. The current stable version is 2.2.22. The library maintains an active release cadence with frequent patch updates, often introducing and refining "experimental" features in dedicated modules while ensuring a stable core. A key differentiator is its deep integration with `fp-ts`, leveraging functional programming paradigms for highly composable type definitions and comprehensive error handling, promoting a type-safe and resilient approach to data processing.