---
title: "Zod vs Valibot"
slug: "zod-vs-valibot"
category: "comparisons"
tags: ["comparisons", "zod", "valibot", "typescript", "validation", "json-schema"]
status: "stable"
last_updated: 2026-05-14
summary: "Pick Zod for ecosystem reach and tRPC integration on a Node app; pick Valibot when bundle size matters, like an edge worker or a browser-shipped form library."
related: ["[[coding/typescript-runtime-validation]]", "[[coding/typescript]]", "[[comparisons/prisma-vs-drizzle]]", "[[ai-agents/structured-output]]", "[[frontend/react-forms]]", "[[coding/index]]"]
---

## Overview

Use Zod when the validator lives on the server, integrates with tRPC, Prisma, or OpenAI structured output, and bundle size is not a top constraint. Use Valibot when the validator ships to a browser, a Cloudflare Worker, or any runtime that pays for every kilobyte. Both produce typed parse results; the split is ecosystem versus bundle. See [[coding/typescript-runtime-validation]] for the validator-agnostic rule set.

## When Zod wins

Zod is the right pick when ecosystem integration drives the decision, or when the validator runs on a long-lived Node or Bun server.

- tRPC, Hono, and Next.js Server Actions all assume Zod schemas. Plugging Valibot in costs adapters or custom serializers.
- Prisma's runtime validators, OpenAI's `zodResponseFormat`, and most LangChain output parsers accept Zod schemas directly.
- The ecosystem is large: `zod-to-openapi`, `zod-to-json-schema`, `react-hook-form` resolver, and form library coverage all default to Zod first.
- Error formatting is mature: `z.flatten()` and `z.format()` produce the shapes form libraries expect without a wrapper.
- Coercion and transforms are first-class: `z.coerce.date()`, `.transform()`, and `.pipe()` cover most parsing pipelines without a second library.
- One canonical answer per pattern; teams onboard in a day.

## When Valibot wins

Valibot is the right pick when the validator runs in a browser bundle, a serverless edge function, or any constrained runtime.

- Bundle size: Valibot's tree-shakable design ships 1 to 5 KB of validator code for a typical form schema. The same Zod schema is 12 to 14 KB gzipped because Zod is a class API.
- Tree-shaking is real: importing `object`, `string`, and `email` brings only those functions. Zod ships the whole class hierarchy.
- Functional API: `parse(schema, value)` is a free function. Each validator is a pure function you can compose without `this` binding.
- Edge worker fit: a Valibot validator inside a Cloudflare Worker keeps the bundle under the 1 MB limit when Zod would push past it.
- Performance: Valibot is 1.5 to 3 times faster than Zod on cold paths because it avoids class instantiation.
- Newer; the API has fewer historical compromises around legacy versions.

## Trade-offs at a glance

| Dimension          | Zod                                      | Valibot                                 |
| ------------------ | ---------------------------------------- | --------------------------------------- |
| API style          | Class chaining (`z.string().email()`)    | Functional pipes (`pipe(string(), ...)`) |
| Bundle (gzipped)   | 12 to 14 KB                              | 1 to 5 KB depending on schema           |
| Tree-shaking       | Limited                                  | Full                                    |
| Speed              | Baseline                                 | 1.5 to 3x faster                        |
| tRPC integration   | Native                                   | Adapter required                        |
| OpenAI structured  | Native (`zodResponseFormat`)             | JSON Schema converter                   |
| Prisma validators  | First-party                              | Community                               |
| Form libraries     | First-class resolvers                    | Newer; smaller resolver coverage        |
| Error format       | `flatten`, `format` built-in             | `flatten` built-in; less mature         |
| Coercion           | `z.coerce.*`                             | `pipe(string(), transform(...))`        |
| JSON Schema export | `zod-to-json-schema`                     | `valibot-to-json-schema`                |
| Hiring familiarity | High                                     | Lower; team needs a brief ramp          |

## Migration cost

Zod-to-Valibot is the common direction once a project ships validators to the browser or edge. The reverse is rare.

- Zod to Valibot: rewrite each schema with the pipe API. The shape and field names match; only the API changes. Plan one engineer-day per 50 schemas. A codemod handles roughly 70 percent.
- Valibot to Zod: equally mechanical; usually triggered by an integration that only ships a Zod adapter. Plan one engineer-day per 50 schemas.
- Cheaper path: keep Zod on the server, use Valibot only for code that ships to the browser or worker. The two coexist fine because neither manipulates global state.

## Recommendation

- New tRPC or Next.js Server Action app: Zod. The integration story alone justifies it.
- New library that ships to npm and will be imported by browser apps: Valibot. Your users will thank you.
- Cloudflare Worker, Vercel Edge, or Lambda function with a tight bundle: Valibot.
- OpenAI structured output, function calling, or RAG pipelines on the server: Zod; see [[ai-agents/structured-output]].
- React form validation with `react-hook-form`: Zod, until Valibot's resolver coverage catches up; see [[frontend/react-forms]].
- Existing Zod codebase, no bundle pain: stay on Zod; the upgrade is not free and the ecosystem is wider.

## Related

- [[coding/typescript-runtime-validation]]
- [[coding/typescript]]
- [[ai-agents/structured-output]]
- [[frontend/react-forms]]
- [[coding/index]]