APK

An APK, or Android application package, is the file format used by Android to distribute and install applications. It is a ZIP-compatible archive that contains the app’s compiled code, resources, assets, and a manifest file required by the Android system.

Contents and structure: The package includes classes.dex (the Dalvik/ART bytecode), AndroidManifest.xml, resources.arsc, and the resources and assets directories. Optional large assets may be packaged as OBB files. APKs can be delivered as a single file or as split APKs, or via Android App Bundles that generate device-specific APKs for installation.

Creation and signing: APKs are built from source code and resources and are signed with a developer’s certificate. The signature enables the package manager to verify authenticity and integrity before installation. Release builds use a private key, while debug builds use a non-production certificate.

Distribution and installation: APKs are distributed through Google Play, other app stores, or direct downloads from developers. On modern Android versions, installing apps from outside official stores requires user permission and enabling the option to install unknown apps. Google Play often serves device-optimized APKs through app bundles and dynamic delivery.

Security and usage considerations: APKs from untrusted sources can carry malware. Users should download from trusted stores, review requested permissions, and keep devices updated. Security features such as Google Play Protect help assess apps, but users remain responsible for verifying publisher integrity and source suitability.