401 Unauthorized error when accessing webapi from angular - angularjs

Question

I need to capture a user's domain\username when they access my webapi app. On my dev machine I have my webapi at localhost:10570 and my angularjs website which makes calls to the webservice at localhost:34575.
If I make a call directly to my webapi app everything works fine. I can see the users domain and username and the service returns the requested data as JSON. But if I access my angularjs site and angular makes the call to webapi then I get 401 unauthorized for every call against the service.
In my WebApi app's web.config I have:
<system.web>
<compilation debug="true" targetFramework="4.5.2" />
<httpRuntime targetFramework="4.5.2" />
<authentication mode="Windows" />
</system.web>
<system.webServer>
<httpProtocol>
<customHeaders>
<add name="Access-Control-Allow-Origin" value="http://localhost:34575" />
<add name="Access-Control-Allow-Methods" value="POST, PUT, DELETE, GET, OPTIONS" />
<add name="Access-Control-Allow-Headers" value="content-Type, accept, origin, X-Requested-With, Authorization, name" />
<add name="Access-Control-Allow-Credentials" value="true" />
</customHeaders>
</system.webServer>
I have this in IIS Express for Visual Studio 2015's applicationhost.config file:
<location path="MyNamespace.WebAPI">
<system.webServer>
<security>
<authentication>
<windowsAuthentication enabled="true" />
<anonymousAuthentication enabled="false" />
</authentication>
</security>
</system.webServer>
</location>
My angularjs site is part of the same solution at "MyNamespace.Client".
Why does accessing the web service directly work fine, but accessing it via the angular app fail?

Answer 1

I didn't realize you have to tell Angular to send your credentials to the server. I just had to change my API calls from:
$http.get(url);
to
$http.get(url, { withCredentials: true });