Each Android version is assigned a unique integer identifier, called the API Level.
As the Android platform evolves and new Android versions are released, each Android version is assigned a unique integer identifier, called the API Level. Because users install apps on older as well as the most recent versions of Android, real-world Android apps must be designed to work with multiple Android API levels.
Each release of Android goes by multiple names:
- The Android version, such as Android 4.4
- The API level, such as "API Level 19"
- A dessert name, such as "KitKat"
Each Android device supports exactly one API level – this API level is guaranteed to be unique per Android platform version. The API level exactly identifies the version of the libraries that your app can call into; it identifies the combination of manifest elements, permissions, etc. that you code against as a developer. Android's system of API levels helps Android determine whether an application is compatible with an Android system image prior to installing the application on a device. When an application is built, it contains the following API level information:
- The target API level of Android that the app is built to run on.
- The minimum API level of Android that is required to run the app.
These settings are used to ensure that the functionality needed to run the app correctly is available on the Android device at installation time. If not, the app is blocked from running on that device. For example, if the API level of an Android device is lower than the minimum API level that you specify for your app, the Android device will prevent the user from installing your app.
