API and Web services serve as a means of communication, but web services and APIs are two of those overlapping tech terms that regularly get confused. You might have heard these words used interchangeably, but are they even the same or two different concepts. Let's understand this by comparing a few points:
| Point of Distinction | API | Web Service |
|---|---|---|
| 1. Definition | An API, or Application Programming Interface, is a set of definitions and protocols that allow one application to communicate with another application. | A web service is either: a service offered by an electronic device to another electronic device, communicating with each other via the Internet, or a server running on a computer device, listening for requests at a particular port over a network, serving web documents (HTML, JSON, XML, images). |
| 2. Need of Network | APIs can be online or offline | Web services are accessed through a network connection only. |
| 3. Type | All APIs are not web services. | All Web Services are API because it exposes an application's data and/or functionality. In other words, A web service is just an API wrapped in HTTP. |
| 4. Light Weight Architecture | APIs have lightweight architecture and are suitable for limited bandwidth devices, like mobile devices. | Web Services require SOAP protocol to send and receive data over the network, so it is not lightweight architecture. |
| 5. Style of Communication | APIs are used for any style of communication. | Web services usually use SOAP (but sometimes REST, UDDI, and XML-RPC). |
| 6. Protocol | APIs provide support for the HTTP and HTTPS protocols | Web Services only support the HTTP protocol |
| 7. Support for XML or JSON | APIs support both XML and JSON | Web Services only support XML |
| 8. Open Source | Many APIs are open source and publicly available with documentation and can be used by the client that understands XML or JSON. | Web Services are not open source but can be used by any client that understands XML. They tend to offer specific data and/or functionality to particular partners. |
| 9. Compression | In API, Data can be compressed. | Web Services uses HTML requests that can be compressed, but XML data cannot be compressed. |
| 10. Specifications | An API is a complete set of rules and specifications that follow to facilitate the interaction. | Web Services does not have a complete set of specifications, and sometimes it cannot perform all the functions that the API can execute. |
