Ascertain

Zero-dependency JavaScript schema validator that compiles native JS values into fast validator functions. Current stable version is 3.2.44. Released regularly (multiple versions per month). Key differentiators: faster than AJV and dramatically faster than Zod for all-errors validation, JavaScript-native schemas (constructors, literals, arrays, objects), compiled validators with first-error and all-errors modes, full TypeScript support with type inference, zero dependencies, and support for Standard Schema v1 for interoperability with tRPC and TanStack Form.