nestjs-guards-interceptors

Authentication guards in NestJS enforce login requirements by implementing CanActivate and validating tokens or sessions before route access. Guards inspect ExecutionContext, verify JWT, session, or API key credentials, and either allow or reject requests based on validation results.

Guards determine whether a request proceeds to a handler using CanActivate logic; interceptors transform, log, or handle errors before and after execution. Guards enforce access control; interceptors shape data and manage cross-cutting concerns like logging and response formatting.

Role-based authorization in NestJS uses guards to extract user roles from ExecutionContext, compare them against required permissions, and deny access if the user lacks necessary roles. Combine metadata decorators with CanActivate guards to enforce RBAC per route.

Yes, NestJS supports multi-strategy authentication by composing multiple guards or implementing a single guard that tries JWT, session, and API key validation sequentially. Guards access ExecutionContext to extract credentials from headers, cookies, or query parameters for each strategy.

Interceptors log HTTP requests and responses by implementing NestInterceptor, accessing ExecutionContext, and using RxJS operators to capture and record data before and after handler execution. Centralize logging logic in a reusable interceptor applied globally or per route.

NestJS guards support JWT token validation, session-based authentication, and API key verification. Each pattern uses ExecutionContext to extract credentials from Authorization headers, cookies, or custom headers, then validate against stored secrets or databases.