How to identify specific request came at HTTP Interceptor using Angular 5?

You can check the if the req.url is equal to the path you want to exclude like below:

  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    // put this before your current code
    if (req.url.indexOf('/* the api path you want to exclude*/') === -1) {
      return next.handle(req);
    }
    // do your stuff here.
    return next.handle(req);
  }

You can add a condition based on your req.url like this:

intercept (req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    if (!req.url.includes('/some/url-to-be-escaped') {
        // Do nothing
        return next.handle(req);
    }

    this.loadingIndicatorService.showLoader();
    this.customAuthorizationHeader();
    const apiRequest = req.clone({headers:this.headers});
    // The rest of your stuff

    return next.handle(req);
}

Hope it helps.

We can do in above ways like check for URL in interceptor itself,but later if we modify the URL like login to sign in,and signup to join or so.This way of implementation will cause side effect.Or overload the interceptor if we have multiple type of logins/un-authenticated pages.

So i suggest We can use an user defined "InterceptorSkipHeader" from login/signup kind of services

unAuthenticatedAPI(someUrl){
    const headers = new HttpHeaders().set(InterceptorSkipHeader, '');
    this.httpClient.get<ResponseType>(someUrl, { headers });
}

And in interceptor you can just check for request with these header and exclude authenticantion

    intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {    
       if (!req.headers.has(InterceptorSkipHeader)) {
         // set token here.
         const apiRequest = req.clone({headers:this.headers})
       }    
       return next.handle(req);
    }