Guards & Authentication

Create a guard

A guard is a class implementing CanActivate. Return true to allow, false to reject.

import { Injectable, CanActivate, ExecutionContext } from '@nestjs/common';

@Injectable()
export class JwtGuard implements CanActivate {
  canActivate(context: ExecutionContext): boolean {
    const request = context.switchToHttp().getRequest();
    const token = request.headers.authorization?.split(' ')[1];
    if (!token) return false;
    try {
      // verify token
      return true;
    } catch {
      return false;
    }
  }
}

Apply a guard

Use @UseGuards() decorator on routes or controllers.

@UseGuards(JwtGuard)
@Get('profile')
getProfile(@Request() req) {
  return req.user;
}

// or on the controller
@Controller('admin')
@UseGuards(JwtGuard)
export class AdminController { ... }

Passport.js integration

NestJS ships with @nestjs/passport for seamless authentication—JWT, OAuth, local, etc.