# Valibot — Modular Schema Validation for TypeScript

> Valibot is a TypeScript-first schema validation library with a modular architecture that produces bundle sizes up to 98% smaller than alternatives while providing comparable type safety.

## Install

Save in your project root:

# Valibot — Modular Schema Validation for TypeScript

## Quick Use
```bash
npm install valibot
```
```typescript
import * as v from "valibot";
const UserSchema = v.object({
  name: v.pipe(v.string(), v.minLength(2)),
  email: v.pipe(v.string(), v.email()),
  age: v.pipe(v.number(), v.minValue(0)),
});
const result = v.safeParse(UserSchema, data);
```

## Introduction
Valibot is a schema validation library for TypeScript created by Fabian Hiller. Its key innovation is a modular, tree-shakable API design: instead of chaining methods on a class, each validation function is a standalone import. This means bundlers can eliminate unused code, producing validation bundles that are a fraction of the size of traditional libraries like Zod.

## What Valibot Does
- Validates data against schemas with full TypeScript type inference
- Produces minimal bundle sizes through function-level tree shaking
- Supports objects, arrays, unions, intersections, tuples, and recursive types
- Provides transformations (coercion, defaults, mapping) within the schema pipeline
- Works in Node.js, Deno, Bun, browsers, and edge runtimes

## Architecture Overview
Valibot uses a pipe-based composition model. A schema is defined with a base type function (e.g., `v.string()`) and refined through `v.pipe()` which chains validation actions (`v.minLength`, `v.email`) and transformations. Each function is a separate ES module export, so bundlers tree-shake everything not explicitly imported. The parse step walks the pipe sequentially, collecting issues into a typed error array on failure or returning the validated and transformed value on success.

## Self-Hosting & Configuration
- Install via npm, pnpm, or yarn—no peer dependencies required
- Zero configuration needed—import and use directly in any TypeScript project
- Works with any bundler (Vite, Webpack, esbuild, Rollup) for tree shaking
- Integrates with form libraries via `@valibot/to-json-schema` for JSON Schema export
- Adapters available for React Hook Form, TanStack Form, and SvelteKit

## Key Features
- Bundle size under 1 KB for common schemas vs. 12+ KB for equivalent Zod schemas
- Full TypeScript type inference with `v.InferOutput<typeof schema>` helper
- Pipe-based composition for chaining validations and transformations
- Async validation support for database lookups and API checks
- Internationalization-ready error messages with custom error functions

## Comparison with Similar Tools
- **Zod** — method-chaining API with larger bundle; Valibot is modular with 98% smaller bundles
- **Yup** — older library with mutable schema builders; Valibot is immutable and tree-shakable
- **AJV** — JSON Schema-based validator; Valibot uses TypeScript-native schemas with better DX
- **io-ts** — fp-ts-based codecs; Valibot is simpler with no functional programming prerequisites
- **Effect Schema** — part of the Effect ecosystem; Valibot is standalone with minimal API surface

## FAQ
**Q: Should I use Valibot or Zod?**
A: If bundle size matters (client-side validation, edge functions), Valibot's modular design produces much smaller bundles. If you prefer method chaining and a larger ecosystem, Zod is well-established.

**Q: Does Valibot work with React Hook Form?**
A: Yes. Use the `@valibot/resolver` package with React Hook Form for schema-based form validation.

**Q: Can I generate JSON Schema from Valibot schemas?**
A: Yes. The `@valibot/to-json-schema` package converts Valibot schemas to JSON Schema for OpenAPI or other uses.

**Q: How does Valibot handle optional and nullable fields?**
A: Use `v.optional()` for fields that may be undefined and `v.nullable()` for null values. They compose naturally with other schema types.

## Sources
- https://github.com/fabian-hiller/valibot
- https://valibot.dev

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Source: https://tokrepo.com/en/workflows/ca2020c1-3ba8-11f1-9bc6-00163e2b0d79
Author: AI Open Source