APIlevel

APilevel is a measure used in software development to describe the version of an application programming interface (API) that a component, library, or application supports or requires. It serves as a contract between producers and consumers of software, indicating which features, functions, and behavioral guarantees are available and compatible across releases.

APilevel can be numeric or symbolic depending on the platform, and may be distinct from the product’s release version. It is used to manage compatibility across platforms and releases by enabling tooling to perform checks, gate features, and prevent runtime or build errors when a component relies on newer APIs than those available in the consumer environment.

In practice, APilevel is tracked in build configurations and manifests. For example, many ecosystems distinguish between a compile-time API level, a minimum required API level, and a targeted API level that the software has been tested against. The compile API level determines which APIs are accessible during compilation, while the minimum API level defines the oldest platform version on which the component is expected to run, and the target API level reflects the platform version used for testing and optimization.

Examples include Android API levels, where developers specify minimum and target API levels, and web APIs that evolve through version numbers (such as v1, v2) to indicate compatibility and feature sets. APilevel concepts also influence deprecation policies and migration strategies, guiding developers in maintaining backward compatibility while adopting new functionality.

See also API versioning, deprecation policy, semantic versioning.