Zod: The Complete Validation Guide for Next.js and TypeScript

Zod: The Complete Validation Guide for Next.js and TypeScript Zod is the standard for runtime validation in modern TypeScript apps. Here's everything you need — from basic schemas to form validation to API input parsing. Why Zod TypeScript types are erased at runtime. A string type annotation doesn't prevent someone from sending a number to your API route. Zod validates at runtime and infers TypeScript types from the same schema — one source of truth for both concerns: import { z } from 'zod'; const UserSchema = z.object({ email: z.string().email(), age: z.number().int().min(18), }); // TypeScript type inferred from schema — no duplicate definition type User = z.infer<typeof UserSchema>; // Runtime validation const result = UserSchema.safeParse({ email: 'bad', age: 15 }); if (!result.success) { console.log(result.error.flatten()); // { fieldErrors: { email: ['Invalid email'], age: ['Number must be >= 18'] } } } Core Primitives z.string() // string z.number() // number z.boolea