JSON Schema vs Zod vs Yup: Choosing the Right Validation Library

JSON Schema, Zod, and Yup are three major approaches to data validation. JSON Schema is a language-agnostic specification, Zod is a TypeScript-first schema library, and Yup is a JavaScript validation library popular in the React ecosystem. This guide compares their approaches, syntax, performance, and ecosystem to help you choose the right tool. Use our JSON Schema Generator, JSON to Zod Schema, and JSON to Yup Schema converters to switch between them.

Feature Comparison

Feature	JSON Schema	Zod	Yup
Language	Any (JSON-based)	TypeScript	JavaScript / TypeScript
Schema format	JSON object	Chainable API / object	Chainable API
Type inference	Third-party tools	First-class (z.infer)	InferType
Bundle size	Varies by implementation	~12 KB (min+gzip)	~25 KB (min+gzip)
Runtime validation	Yes	Yes (zero dependencies)	Yes
Async validation	No (sync only)	Yes	Yes
Custom error messages	Via library	Built-in	Built-in
Cross-platform	All languages	TypeScript/JavaScript	JavaScript

Validation Syntax Comparison

// Schema: User with name, email, age, and tags

// JSON Schema
{
  "type": "object",
  "properties": {
    "name": { "type": "string", "minLength": 2 },
    "email": { "type": "string", "format": "email" },
    "age": { "type": "integer", "minimum": 18, "maximum": 120 },
    "tags": {
      "type": "array",
      "items": { "type": "string" },
      "minItems": 0
    }
  },
  "required": ["name", "email"]
}

// Zod
import { z } from 'zod';
const UserSchema = z.object({
  name: z.string().min(2, 'Name must be at least 2 characters'),
  email: z.string().email('Invalid email format'),
  age: z.number().int().min(18).max(120).optional(),
  tags: z.array(z.string()).default([])
});
type User = z.infer;

// Yup
import * as yup from 'yup';
const UserSchema = yup.object({
  name: yup.string().min(2, 'Name must be at least 2 characters').required(),
  email: yup.string().email('Invalid email format').required(),
  age: yup.number().integer().min(18).max(120).nullable(),
  tags: yup.array().of(yup.string()).default([])
});

Advanced Validation Patterns

// Conditional validation
// If user type is "business", companyName is required

// JSON Schema (if/then/else)
{
  "if": { "properties": { "type": { "const": "business" } } },
  "then": { "required": ["companyName"] },
  "else": { "required": ["personalName"] }
}

// Zod (refine/discriminatedUnion)
const UserSchema = z.discriminatedUnion('type', [
  z.object({ type: z.literal('personal'), personalName: z.string() }),
  z.object({ type: z.literal('business'), companyName: z.string() })
]);

// Yup (when)
yup.object({
  type: yup.string().oneOf(['personal', 'business']).required(),
  companyName: yup.string().when('type', {
    is: 'business',
    then: (schema) => schema.required()
  }),
  personalName: yup.string().when('type', {
    is: 'personal',
    then: (schema) => schema.required()
  })
});

Type Inference

// JSON Schema: Must use external tools
// json-schema-to-typescript generates:
// export interface User { name: string; email: string; age?: number; tags?: string[]; }

// Zod: Built-in type inference
const UserSchema = z.object({ name: z.string(), email: z.string().email() });
type User = z.infer;
// type User = { name: string; email: string; }

// Yup: Limited inference
import { InferType } from 'yup';
type User = InferType;
// Basic types but less accurate for complex schemas

Performance Benchmarks

Operation	JSON Schema (Ajv)	Zod	Yup
Simple object validation	~50K ops/s	~200K ops/s	~80K ops/s
Nested object (3 levels)	~30K ops/s	~120K ops/s	~50K ops/s
Array of objects (10 items)	~15K ops/s	~60K ops/s	~25K ops/s
String parsing/coercion	~40K ops/s	~150K ops/s	~60K ops/s

When to Use Each

Use Case	Recommended	Why
Cross-language validation	JSON Schema	Works with any language, not just JS/TS
TypeScript-first project	Zod	Best type inference, smallest bundle
React form (Formik)	Yup	Native Formik integration
API request validation (backend)	JSON Schema or Zod	JSON Schema for polyglot, Zod for Node.js
Configuration file validation	JSON Schema	Supported by VS Code, many editors
Runtime type checking	Zod	Parse don't validate pattern

Converting Between Schema Formats

Our tools make it easy to convert between formats:

• JSON Schema Generator — Generate JSON Schema from data
• JSON to Zod Schema — Generate Zod from JSON samples
• JSON to Yup Schema — Generate Yup from JSON samples

Next Steps

Choose your validation approach and use our generators: JSON Schema, Zod Schema, or Yup Schema.