Zod vs Yup vs Joi — TypeScript Validation Comparison
Choosing a validation library for TypeScript? Compare Zod, Yup, and Joi across type safety, bundle size, performance, and ecosystem integration to find the best fit for your project.
JSON to Zod Converter
Convert JSON or JSON Schema to Zod validation schemas. Supports $ref, allOf/oneOf/anyOf, enum, format constraints, and nested objects.
About JSON to Zod Converter
- Two input modes — paste raw JSON data to infer schemas, or paste a JSON Schema for precise conversion with
$ref,allOf/oneOf/anyOf, and constraints. - JSON Schema support — converts
required,enum,const,format(email, uri, uuid, date-time, ipv4, ipv6),pattern,minimum/maximum,minLength/maxLength,default, and$defs/definitions. - Smart inference — detects emails, URLs, UUIDs, and ISO dates in raw JSON values and adds appropriate Zod refinements.
- Required vs optional — JSON Schema
requiredarrays map to required fields; all others get.optional(). - TypeScript type — generates
z.infer<typeof schema>so you get TypeScript types for free. - Everything runs in your browser — no data is sent over the network.
Type inference comparison
Zod: First-class TypeScript inference via z.infer — every schema automatically produces the correct TypeScript type, including unions, intersections, optionals, and transforms. Yup: InferType<typeof schema> exists but has known edge cases with nullable/optional fields and transforms. Joi: No official TypeScript type inference — you must manually write interfaces that mirror your schemas, creating a maintenance burden and drift risk.
Bundle size and performance
Zod: ~13KB minified+gzipped. Yup: ~12KB minified+gzipped. Joi: ~30KB+ minified+gzipped (designed for Node.js, not optimized for browsers). For frontend applications, Zod and Yup are comparable in size. Joi is significantly larger and was designed for server-side use. Performance is similar for typical validation workloads — the difference is negligible for most applications.
When to use each library
Use Zod for new TypeScript projects, especially with tRPC, Next.js, or React Hook Form — it has the best TypeScript integration and fastest-growing ecosystem. Use Yup if you have an existing Formik-based codebase — Formik was built around Yup and migration would be costly. Use Joi for Node.js-only backends where you need extensive validation features and don't need TypeScript type inference.
Frequently Asked Questions
Should I migrate from Yup to Zod?
If you rely on z.infer for type safety across your app, the migration is worthwhile. If you only use Yup for form validation with Formik and don't need type inference, the migration cost may not justify the benefit. For new features, consider using Zod alongside Yup and gradually migrating.
Which validation library has the most downloads?
Zod leads with 90M+ weekly npm downloads (as of early 2026), followed by Joi at ~10M and Yup at ~6M. Zod's growth has been explosive — it surpassed both Joi and Yup in 2024 and continues to accelerate.
Can I use Zod and Yup together in the same project?
Yes. They are independent libraries with no conflicts. This is a practical migration strategy: use Zod for new code and tRPC/API layers while keeping Yup for existing Formik forms. Gradually replace Yup schemas as you touch those files.
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