Angular - Unhandled Navigation Error after building

Using Angular routing engine will force you to host your app in some server (e.g. IIS, NodeJS etc.)

A simple angular app without routes can run without hosting it on a server.

From Angular docs:

Angular apps are perfect candidates for serving with a simple static HTML server. You don't need a server-side engine to dynamically compose application pages because Angular does that on the client-side.

If the app uses the Angular router, you must configure the server to return the application's host page (index.html) when asked for a file that it does not have.

Angular routing works if you use hash routing and define your base href as follows in your index.html.

<base href="#">