APIs

APIs Make Life Easier for Developers

Let’s say you want to develop an app for an iPhone. Apple’s iOS operating system provides a large number of APIs—as every other operating system does—to make this easier on you.

If you want to embed a web browser to show one or more web pages, for example, you don’t have to program your web browser from scratch just for your application. You use the WKWebView API to embed a WebKit (Safari) browser object in your application.

APIs Control Access to Resources

APIs are also used to control access to hardware devices and software functions that an application may not necessarily have permission to use. That’s why APIs often play a big role in security.

For example, if you’ve ever visited a website and seen a message in your browser that the website is asking to see your precise location, that website is attempting to use the Geolocation API in your web browser. Web browsers expose APIs like this to make it easy for web developers to access your location—they can just ask “where are you?” and the browser does the hard work of accessing GPS or nearby Wi-Fi networks to find your physical location.

However, browsers also expose this information via an API because it’s possible to control access to it. When a website wants access to your exact physical location, the only way they can get it is via the location API. And, when a website tries to use it, you—the user—can choose to allow or deny this request. The only way to access hardware resources like the GPS sensor is through the API, so the browser can control access to the hardware and limit what apps can do.

This same principle is used on modern mobile operating systems like iOS and Android, where mobile apps have permissions that can be enforced by controlling access to APIs. For example, if a developer tries to access the camera via the camera API, you can deny the permission request and the app has no way of accessing your device’s camera.

File systems that use permissions—as they do on Windows, Mac, and Linux—have those permissions enforced by the file system API. A typical application doesn’t have direct access to the raw physical hard disk. Instead, the app must access files through an API.