How do interceptors handle errors vs exception filters in NestJS — what is the division of responsibility?

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// Interceptor — remap domain errors to HTTP errors (runs first)
@Injectable()
export class DomainToHttpInterceptor implements NestInterceptor {
  intercept(ctx: ExecutionContext, next: CallHandler): Observable<any> {
    return next.handle().pipe(
      catchError(err => {
        if (err instanceof QueryFailedError)
          throw new BadRequestException(err.message);
        if (err instanceof EntityNotFoundError)
          throw new NotFoundException(err.message);
        throw err; // pass unknown errors to filters
      }),
    );
  }
}

// Filter — shape final error response (runs after interceptors)
@Catch(HttpException)
export class HttpExceptionFilter implements ExceptionFilter {
  catch(exception: HttpException, host: ArgumentsHost) {
    const res = host.switchToHttp().getResponse();
    res.status(exception.getStatus()).json({
      error: exception.message,
      timestamp: new Date().toISOString(),
    });
  }
} Interceptors (catchError) — translate exception types: EntityNotFoundError → NotFoundException. Exception filters — format the HTTP response: shape JSON body, set headers, log errors. Interceptors run before filters in the pipeline — remap first, then format. Use interceptors when the error type needs changing; use filters when only the response format needs changing. Always re-throw from interceptor catchError if the error is not handled — let the filter catch it.

How do interceptors handle errors vs exception filters in NestJS — what is the division of responsibility?

Interceptors via catchError() remap exceptions between types before filters run — used to translate domain errors into HTTP exceptions. Exception filters shape the HTTP error response sent to the client. Interceptors fix the type of exception; filters fix the format of the response.

How do interceptors handle errors vs exception filters in NestJS — what is the division of responsibility?

Interceptors via catchError() remap exceptions between types before filters run — used to translate domain errors into HTTP exceptions. Exception filters shape the HTTP error response sent to the client. Interceptors fix the type of exception; filters fix the format of the response.

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