Applying middleware to routes in NestJS

Introduction

Middleware helps you run code before your route handles a request. It can check or change requests easily.

You want to log every request to certain routes.

You need to check if a user is logged in before accessing a page.

You want to add headers or modify requests for specific routes.

You want to block requests from certain IP addresses on some routes.

Syntax

NestJS

import { Injectable, NestMiddleware } from '@nestjs/common';
import { Request, Response, NextFunction } from 'express';

@Injectable()
export class MyMiddleware implements NestMiddleware {
  use(req: Request, res: Response, next: NextFunction) {
    // your code here
    next();
  }
}

// In your module
import { MiddlewareConsumer, Module, RequestMethod } from '@nestjs/common';

@Module({
  providers: [MyMiddleware]
})
export class AppModule {
  configure(consumer: MiddlewareConsumer) {
    consumer
      .apply(MyMiddleware)
      .forRoutes('route-path');
  }
}

Middleware class must implement NestMiddleware and have a use method.

Use consumer.apply(...).forRoutes(...) to attach middleware to routes.

Examples

This applies LoggerMiddleware to all requests to the /cats route.

NestJS

consumer.apply(LoggerMiddleware).forRoutes('cats');

This applies AuthMiddleware only to GET requests on /dogs.

NestJS

consumer.apply(AuthMiddleware).forRoutes({ path: 'dogs', method: RequestMethod.GET });

This applies two middleware in order to the /users route.

NestJS

consumer.apply(LoggerMiddleware, AuthMiddleware).forRoutes('users');

This applies middleware to all routes and methods.

NestJS

consumer.apply(MyMiddleware).forRoutes({ path: '*', method: RequestMethod.ALL });

Sample Program

This example creates a simple logger middleware that prints the HTTP method and URL for GET requests to /hello. It shows how to apply middleware to a specific route and method.

NestJS

import { Injectable, NestMiddleware, MiddlewareConsumer, Module, RequestMethod } from '@nestjs/common';
import { Request, Response, NextFunction } from 'express';

@Injectable()
export class LoggerMiddleware implements NestMiddleware {
  use(req: Request, res: Response, next: NextFunction) {
    console.log(`Request to: ${req.method} ${req.url}`);
    next();
  }
}

@Module({
  providers: [LoggerMiddleware]
})
export class AppModule {
  configure(consumer: MiddlewareConsumer) {
    consumer
      .apply(LoggerMiddleware)
      .forRoutes({ path: 'hello', method: RequestMethod.GET });
  }
}

// Assume a controller with GET /hello route exists

Important Notes

Always call next() in middleware to continue the request cycle.

You can apply middleware to multiple routes or methods by passing arrays.

Middleware runs before route handlers, so it can block or modify requests early.

Summary

Middleware runs code before routes handle requests.

Use consumer.apply(...).forRoutes(...) to attach middleware to routes.

Middleware can log, check, or change requests easily.