There are various ways in which you can host your Web API, and you need not always have to host your Web API in IIS. You can host it in a separate process as well.

This article explain to you how you can configure web pages to communicate directly from a paired device via Web Bluetooth API in Edge.

Cross-Origin Resource Sharing in ASP.NET Web API allows cross-domain access to your Web API methods.

Browser makers have agreed to make Mozilla's MDN Web Docs the prime repository for information about web APIs.