What is a public API

What is an API

API is short for Application programming interface, in German an API is a program interface. Developers can access the functions of an application via an API. That is not really exciting in and of itself. It became interesting when Web 2.0 providers such as Amazon or eBay began to offer their internal interfaces via the Internet. Through this opening were out Web sites Platforms to which many thousands of systems can be connected. These interfaces are used to continuously add new items, update prices and sell goods without the need for human interaction. Other examples can be found in social networks. There are countless apps that broadcast messages on Twitter, Facebook and Co. via APIs.

In contrast to a user interface, with an API it is not a person who communicates with a system, but applications communicate directly with one another. For example, I order a printer in an online shop. I myself only communicate with the shop via its web interface. The shop itself can use APIs to:

  • inquire about the creditworthiness of the customer with a credit report
  • take out an extended warranty with an insurance company
  • initiate payment via credit card or PayPal
  • and hire a freight forwarder

The communication required for this runs between different organizations via APIs.

APIs for partners, businesses and the public

Every API has its target audience. External or public APIs are accessible over the Internet and are open to a large number of users. Examples of public APIs are the interfaces of Amazon, eBay, Facebook, Paypal and Google. With the public APIs, the complex web services standards could not prevail. Mainly REST-based services are used there, which make use of the properties of the HTTP protocol. An internal API is only available within a company or organization. Many companies still use web services based on the SOAP standard for their internal APIs. In-house REST APIs are also increasingly being used. APIs for partners make the functionalities of a company accessible via the Internet or via virtual private networks. In contrast to the "Public" APIs, the users are restricted to a smaller group.


A mashup can be created from several APIs. For example, a lightning strike API and the Google Maps API could be used to create a mashup that displays lightning strikes on a map.

A mashup can be created purely with HTML5 and Javascript and executed on a website. A server is not necessary for a mashup.