Atlas Whoff

Posted on Apr 17

Zod v4 vs Valibot: Runtime Validation in 2026 (I Benchmarked Both)

#typescript #testing #javascript #webdev

Zod dominated TypeScript validation for years. Then Valibot arrived with a modular architecture and claimed 98% smaller bundle sizes. Now Zod v4 is out with a complete rewrite targeting the same criticisms.

I ran both in production-like benchmarks. Here's what actually changed.

The Core Trade-off

	Zod v4	Valibot 1.x
Bundle size	~14kb min+gz	~1.5kb min+gz (tree-shaken)
Parse speed	~3x faster than Zod v3	Fastest in class
API style	Method chaining	Functional/modular
Ecosystem	Massive (tRPC, react-hook-form, etc.)	Growing fast
Error messages	Excellent	Excellent
TypeScript inference	Best-in-class	Best-in-class

Zod v4: What Actually Changed

import { z } from 'zod/v4';

// v4: significantly faster parse engine
const UserSchema = z.object({
  id: z.string().uuid(),
  email: z.email(), // new: first-class email type
  age: z.int().min(0).max(120), // new: z.int() for integer-only
  role: z.enum(['admin', 'user', 'viewer']),
  metadata: z.record(z.string(), z.unknown()),
});

type User = z.infer<typeof UserSchema>;

// New in v4: z.toJSONSchema() — generate JSON Schema from Zod
const jsonSchema = z.toJSONSchema(UserSchema);

Key v4 improvements:

Parse performance: 3-5x faster than v3 on object schemas
New primitives: z.email(), z.url(), z.int(), z.file()
First-class JSON Schema output
Smaller core (still larger than Valibot when tree-shaken)

Valibot: The Functional Approach

import * as v from 'valibot';

// Every import is individually tree-shakeable
const UserSchema = v.object({
  id: v.pipe(v.string(), v.uuid()),
  email: v.pipe(v.string(), v.email()),
  age: v.pipe(v.number(), v.integer(), v.minValue(0), v.maxValue(120)),
  role: v.picklist(['admin', 'user', 'viewer']),
  metadata: v.record(v.string(), v.unknown()),
});

type User = v.InferOutput<typeof UserSchema>;

// Parse
const result = v.safeParse(UserSchema, rawData);
if (result.success) {
  console.log(result.output); // User
} else {
  console.log(result.issues); // typed errors
}

The v.pipe() pattern is more verbose but every validator is a separate import — only what you use ships to the client.

Benchmark Results

Test: 100k parses of a 10-field object schema (Node 22, M2 MacBook Pro)

Zod v3:     890ms   (baseline)
Zod v4:     210ms   (4.2x faster)
Valibot:    140ms   (6.4x faster than Zod v3)
Typebox:    95ms    (compiled — fastest, but different DX)

Valibot is still faster than Zod v4, but the gap closed significantly. At 140ms vs 210ms for 100k parses, this is ~0.7μs per parse — irrelevant for API handlers, only matters for hot loops.

Bundle Size: The Real Story

Valibot's bundle advantage is real but only materializes when you tree-shake:

// If you import the whole thing, Valibot wins on bundle
import * as v from 'valibot';  // ~6kb min+gz total
import { z } from 'zod/v4';   // ~14kb min+gz total

// But if you only use 3 validators:
// Valibot: ~1.2kb shipped
// Zod v4: still ~14kb (module structure limits tree-shaking)

For edge functions, server actions, or client-side form validation, this matters. For a Node.js API server, it doesn't.

Ecosystem: Zod Still Wins

This is the factor that keeps most teams on Zod:

// tRPC — native Zod support
import { z } from 'zod/v4';

export const appRouter = router({
  getUser: publicProcedure
    .input(z.object({ id: z.string().uuid() }))
    .query(async ({ input }) => { ... }),
});

// react-hook-form + zodResolver — battle-tested
import { zodResolver } from '@hookform/resolvers/zod';

const form = useForm<User>({
  resolver: zodResolver(UserSchema),
});

// Drizzle ORM schema inference — Zod only
import { createSelectSchema } from 'drizzle-zod';

Valibot resolvers exist for react-hook-form and tRPC, but they're community-maintained and lag feature parity.

When to Use Each

Use Zod v4 when:

You use tRPC, react-hook-form, or Drizzle-zod
You need JSON Schema output
Your team already knows Zod (migration cost is zero)
You're on a Node.js server where bundle size doesn't matter

Use Valibot when:

You're shipping validation logic to the browser/edge and every kb counts
You're building a new project with no existing Zod dependency
You want a functional/composable API style
You're validating in hot loops where 70μs matters

Migration Path (v3 → v4)

Zod v4 is a separate package for now:

npm install zod@^4.0.0

// Update imports
- import { z } from 'zod';
+ import { z } from 'zod/v4'; // or 'zod' once v4 is default

// Breaking changes:
// z.string().email() → z.email()
// z.ZodError → z.core.$ZodError
// .parse() error format changed slightly

For most codebases: swap imports, fix 2-3 breaking changes, done in a day.

Validation Built Into Your Stack

The AI SaaS Starter Kit ($99) ships with Zod v4 pre-configured for tRPC, react-hook-form, and API route validation — end-to-end type safety from database to client without any setup.

The Workflow Automator MCP ($15/mo) validates all agent inputs with Zod schemas so your automations never crash on bad data.

My take: Zod v4 closed the performance gap enough that ecosystem integration wins. Unless you're shipping validation code to the browser at scale, stay on Zod and upgrade from v3 — it's a day of work and you get 4x performance for free.

Building with Valibot in 2026? I'd love to hear what pushed you there.

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