Valibot
Modular TypeScript-first schema validation library designed for minimum bundle size via tree-shaking. Alternative to Zod with similar API but much smaller bundle footprint — under 1KB for simple schemas vs Zod's 10-15KB baseline. Each validator is imported individually enabling aggressive tree-shaking. Standard Schema compliant. Growing alternative for performance-sensitive browser applications.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
MIT licensed. Zero dependencies. Local computation. Input validation library — reduces attack surface.
⚡ Reliability
Best When
Bundle size is critical (browser, edge functions, Cloudflare Workers) and you need TypeScript-first schema validation with type inference.
Avoid When
Bundle size isn't a constraint and you're already using Zod or Joi — Valibot's main advantage is bundle size.
Use Cases
- • Build lightweight form validation in browser applications where bundle size is critical (e-commerce, mobile web)
- • Validate API responses in edge functions or Cloudflare Workers where bundle size directly impacts cold start time
- • TypeScript schema validation with type inference in projects where Zod's bundle size is prohibitive
- • Validate agent configuration and data contracts in bundle-size-sensitive frontend contexts
- • Implement Standard Schema-compliant validation that works across multiple validation ecosystems
Not For
- • Server-side applications where bundle size doesn't matter — Zod or Joi may have better ecosystem support
- • Projects heavily invested in Zod's ecosystem — Valibot's API differs enough to require migration effort
- • Complex async validation — Valibot's async support is more limited than Zod or Yup
Interface
Authentication
Local library — no authentication required. MIT licensed.
Pricing
MIT licensed. Zero cost.
Agent Metadata
Known Gotchas
- ⚠ v1 has breaking API changes from v0.x — parse() became parse() with different import structure; check migration guide if upgrading
- ⚠ Modular imports required for tree-shaking: import { object, string, number, parse } from 'valibot' — not a default import
- ⚠ API differs from Zod — v.string() in Valibot vs z.string() in Zod; not a drop-in replacement despite similar concepts
- ⚠ InferOutput<typeof schema> for TypeScript type inference — not InferType<> like Yup or z.infer<> like Zod
- ⚠ Async validation requires parseAsync() — synchronous parse() throws for schemas with async validators
- ⚠ Ecosystem maturity: fewer integrations and adapters than Zod (less react-hook-form integration, fewer SaaS adapters) — evaluate ecosystem fit for your stack
Alternatives
Full Evaluation Report
Detailed scoring breakdown, competitive positioning, security analysis, and improvement recommendations for Valibot.
Scores are editorial opinions as of 2026-03-06.