Web service and API is different.
The terms web service and application programming interface (API) should not be used interchangeably in every case.
- Web services are a type of application programming interface (API). The opposite is not always true!
- Web services need a network to achieve their objective. APIs can achieve their goal even offline.
- Web services rarely allow external developer access, and there are a lot of APIs that welcome external developer tinkering.
- Web services usually utilize SOAP for security reasons. APIs can be found using different designs, such as XML-RPC, JSON-RPC, SOAP, and REST.
- Web services usually utilize the XML format for data encoding. APIs can be found using different formats to store data, with the most popular being JavaScript Object Notation (JSON).