ValidationPipe Options · DTOs and Validation in NestJS | NestJS

ValidationPipe Options

Turn Validation On Globally

src/main.ts

import { ValidationPipe } from '@nestjs/common';

app.useGlobalPipes(
  new ValidationPipe({
    whitelist: true,              // strip properties without decorators
    forbidNonWhitelisted: true,   // ...or reject the request instead of stripping
    transform: true,              // turn the plain body into a CreateProductDto instance, convert types
    transformOptions: { enableImplicitConversion: true },   // "5" -> 5 for query/params based on TS type
  }),
);

Option	Effect
`whitelist`	Removes unknown fields like `isAdmin` silently
`forbidNonWhitelisted`	Returns 400 if unknown fields are present
`transform`	Gives you real DTO instances and converted primitives
`stopAtFirstError`	Only one message per property
`disableErrorMessages`	Hide details in production (rarely needed)

whitelist in Action

Example

With whitelist: true and forbidNonWhitelisted: true, a client trying to sneak in a field is rejected:

curl -i -X POST http://localhost:3000/products -H "Content-Type: application/json" \
  -d '{"name":"Fire-Boltt Ninja","price":1499,"stock":20,"category":"wearables","isFeatured":true}'

Example output

HTTP/1.1 400 Bad Request
Content-Type: application/json; charset=utf-8

{"message":["property isFeatured should not exist"],"error":"Bad Request","statusCode":400}

Tip: You can also apply validation to one handler only: @Body(new ValidationPipe({ groups: ['admin'] })) dto: CreateProductDto. Global is the usual choice.