zod vs valibot

validation

zod

valibot

Zod and Valibot are TypeScript-first schema validation libraries that provide runtime type checking with static type inference. Zod pioneered the developer-friendly approach to validation in the TypeScript ecosystem with its intuitive method chaining API, while Valibot emerged as a modern alternative designed specifically to address bundle size concerns through functional composition and aggressive tree-shaking.

This comparison matters because validation libraries often become deeply embedded in your codebase—touching forms, API boundaries, configuration parsing, and data transformation layers. Zod targets developers who value ecosystem maturity, extensive integrations (tRPC, React Hook Form, Prisma), and a large community. Valibot appeals to teams building client-side applications where every kilobyte matters, or developers who prefer functional programming patterns over object-oriented method chaining.

Head-to-Head

Bundle Size Impact→ valibot wins

zod

A simple login form validation adds 17.7 kB to your bundle with standard Zod, or 6.88 kB with Zod Mini (tree-shakable variant). The method-chaining architecture creates interdependencies that limit tree-shaking effectiveness across bundlers.

valibot

The same login form validation requires only 1.37 kB—a 90% reduction compared to standard Zod. Valibot's functional composition design allows bundlers to eliminate unused validators effortlessly, making it the clear winner for client-side applications.

API Paradigmtie

zod

Uses object-oriented method chaining (z.string().email().min(5).optional()) which feels natural to developers familiar with jQuery, Lodash, or builder patterns. Validation rules read left-to-right sequentially, though creating custom refinements requires understanding the .refine() and .superRefine() methods.

valibot

Employs functional composition with pipe() for transformations (v.pipe(v.string(), v.email(), v.minLength(5))). This matches functional programming conventions but requires wrapping base types and actions separately. Optional fields require v.optional() wrapper rather than method chaining.

Runtime Validation Speed→ valibot wins

zod

Zod v3 is noticeably slower than Valibot in benchmarks. Zod v4 matches Valibot's runtime performance, but both are significantly outperformed by compiler-based validators like Typia. For most applications, validation is not the bottleneck—network I/O and rendering dominate.

valibot

Approximately 2x faster than Zod v3, with similar performance to Zod v4. Time to Interactive (TTI) benchmarks show exceptional results due to minimal initialization overhead—the library doesn't execute heavy setup code before validating your first schema.

Ecosystem Integration→ zod wins

zod

First-class support from major libraries: tRPC uses Zod as the default validator, React Hook Form has dedicated @hookform/resolvers integration, Prisma generates Zod schemas, and countless form libraries provide Zod adapters. Extensive Stack Overflow coverage and ChatGPT training data.

valibot

Growing but limited third-party integrations. You'll often need to write custom adapters or wait for library authors to add Valibot support. The functional API makes adapter creation straightforward, but you're more likely to be the first person solving integration problems.

Error Handling Granularity→ zod wins

zod

Provides structured error objects with path information, multiple error formatting helpers, and methods like .prettyError() for debugging. The .safeParse() API returns { success: boolean, data?, error? } which integrates cleanly with Result/Either patterns in functional code.

valibot

Returns structured validation issues similar to Zod, but lacks convenience methods like prettyError(). Error customization uses message functions or custom validators. The flatten() utility helps transform nested errors, though documentation is less comprehensive than Zod's error handling guides.

Type System Complexitytie

zod

Handles complex TypeScript scenarios reliably—discriminated unions, recursive schemas, lazy evaluation, and deep inference work consistently. Type inference can be slow on extremely large schemas (200+ fields), though this rarely matters in practice. The z.infer<> utility is well-documented.

valibot

Achieves similar type inference capabilities using v.infer<>, including discriminated unions and recursive types. The functional architecture occasionally requires more explicit type annotations when composing custom validators, but handles standard use cases identically to Zod.

Verdict

Choose Valibot if you're building client-side applications where bundle size directly impacts user experience—single-page apps, mobile web applications, or edge functions with size constraints. The 90% bundle size reduction is not theoretical; it translates to measurably faster page loads on slow networks. Valibot also wins if you're already working in a functional programming style with libraries like fp-ts or Ramda, as the pipe-based API will feel immediately familiar.

Choose Zod for everything else, particularly server-side validation, internal tools, or projects where ecosystem integration saves more development time than bytes saved matter to end users. If you're using tRPC, Prisma, React Hook Form, or other popular tools with native Zod support, fighting against the ecosystem momentum isn't worth the bundle savings. Zod's method-chaining API also has significantly better discoverability—your editor's autocomplete naturally guides you through available validators, whereas Valibot requires more familiarity with available pipe actions.

When to Use Each

If you are building a consumer-facing e-commerce checkout flow → use Valibot because every 10 kB of JavaScript delays interactivity by ~50ms on median mobile connections, directly impacting conversion rates.

If you are building a tRPC API with full-stack type safety → use Zod because tRPC's native integration eliminates boilerplate and the server-side bundle size is irrelevant.

If you are validating configuration files in a Node.js CLI tool → use Zod because the 16 kB difference is negligible in server contexts and the superior error formatting helps users debug invalid config files.

If you are building a lightweight browser extension → use Valibot because extensions have strict size limits (Chrome Web Store warns at 128 MB total) and validation code executes on every page load in content scripts.

Learn More

zod →valibot →

Head-to-Head

Bundle Size Impact→ valibot wins

zod

valibot

API Paradigmtie

zod

valibot

Runtime Validation Speed→ valibot wins

zod

valibot

Ecosystem Integration→ zod wins

zod

valibot

Error Handling Granularity→ zod wins

zod

valibot

Type System Complexitytie

zod

valibot

Verdict

When to Use Each

If you are building a tRPC API with full-stack type safety → use Zod because tRPC's native integration eliminates boilerplate and the server-side bundle size is irrelevant.