Valibot is a schema validation library for TypeScript built around a modular design. Instead of shipping one large object with every method attached, it exposes individual functions for strings, numbers, objects, arrays, dates and custom checks that can be composed into a schema. A bundler then includes only the pieces an application actually imports, which makes the library particularly attractive for front-end code where every kilobyte of shipped JavaScript matters.
The type safety story is a central part of the design. Schemas infer static TypeScript types in both directions, so a single definition can be used to validate unknown input at runtime and to derive the type used throughout the rest of the codebase. Validation pipelines support transformations, refinements, async checks, default values and detailed issue objects, and error messages can be supplied per schema or localised for different languages, which is useful for public-facing forms.
It suits teams validating user input in React, Vue or Svelte applications, developers checking request bodies at the boundary of a Node or edge API, and library authors who want a small dependency with predictable inference. Projects that already model their domain with TypeScript often find that replacing duplicated interface declarations and hand-written guards with one schema reduces drift between compile-time assumptions and the data that actually arrives.
Compared with Zod, Valibot deliberately trades a single fluent API for a functional composition model and a noticeably smaller bundle; Zod remains convenient when a project wants the most familiar chainable syntax and the widest ecosystem of extensions. Compared with Yup, Valibot offers tighter TypeScript inference without ambient type declarations. Compared with JSON Schema validators such as Ajv, it is more idiomatic inside TypeScript code, though JSON Schema remains better when schemas must be shared across languages or published as a contract.
Because the API is organised as many small imports, pinning the package version and reading the migration notes before upgrading is advisable. Async validations should be ordered deliberately, since they can change both latency and which issues are reported first. For security-sensitive boundaries, validate at the edge of the system and treat the inferred type as evidence about parsed data, not as proof about unvalidated input from a third party.