Input Validation in TypeScript APIs: Zod vs Joi vs Class-Validator

Input Validation in TypeScript APIs: Zod vs Joi vs Class-Validator Your API accepts a POST body. You trust it. A user sends { "age": "not a number" }. Your database query fails. Or worse, it succeeds with bad data. Why Validate at the Boundary TypeScript types disappear at runtime. req.body is any . Your internal functions trust typed parameters, but the data crossing your API boundary is untyped. Validate once at the edge, trust everywhere inside. Zod (Recommended) Schema-first. TypeScript-native. Infers types from schemas: import { z } from " zod " ; const CreateUserSchema = z . object ({ name : z . string (). min ( 1 ). max ( 100 ), email : z . string (). email (), age : z . number (). int (). min ( 13 ). max ( 150 ), role : z . enum ([ " user " , " admin " ]). default ( " user " ), }); type CreateUser = z . infer < typeof CreateUserSchema > ; app . post ( " /users " , ( req , res ) => { const result = CreateUserSchema . safeParse ( req . body ); if ( \ ! result . success ) return r