What is the basic difference between WebApi over WCF/Web Services?

Web API

• This is the new framework for building HTTP services the easy and simple way.
• Web API is open source an ideal platform for building RESTful services using the .NET Framework.
• Unlike a WCF REST service, it use the full features of HTTP (like URIs, request/response headers, caching, versioning, various content formats).
• It also supports the MVC features such as routing, controllers, action results, filter, model binders, IOC container or dependency injection, unit testing that makes it more simple and robust.
• It can be hosted within the application or on IIS.
• It is a light weight architecture and good for devices which have limited bandwidth like smart phones.

Web Service

• It is based on SOAP or REST and returns data in XML format.
• It supports only the HTTP protocol.
• It is not open source but can be consumed by any client that understands XML.