In a nutshell: Android’s kernel is based on the long-term support branches of the Linux kernel. LTS releases are essential for the well-being of Google’s mobile OS, so much so that the company decided to extend the support period beyond what was already guaranteed by Linux developers.
Google recently updated official documentation on Android Common Kernels (ACK) with new support lifetime pledges and refreshed end-of-life (EOL) dates for currently supported kernels. ACKs are the main branches of the Android Open Source Project (AOSP), which includes Google’s own Android implementations for third-party companies working in the Android ecosystem.
Starting in 2017, Linux developers decided to provide six years of support for LTS releases. That decision was later revised, bringing the support period back down to two years. The LTS Linux kernel is an essential codebase for Android, as Google selects the most secure open-source kernel while adding additional functionality and vendor-specific features required by Android devices.
The ACK-Linux LTS relationship is now strengthening thanks to Google’s direct involvement. The company will provide additional support to stable LTS kernels, with most Android versions now being supported for four years or more. Android 14, which is based on the Linux 6.1 LTS branch, will be supported until 2029. Meanwhile, the Android 15 kernel (Linux LTS 6.6) will be supported until 2028.
The new support policy will impose additional requirements on third-party vendors. OEM manufacturers launching phones based on Android 15 or later will now be required to use either the 6.1 or 6.6 LTS branch of the Linux kernel.
Linux LTS is regularly maintained with security patches and bug fixes, but it doesn’t include the latest (and potentially unstable) features introduced in non-LTS kernel branches.
Google’s official documentation clearly states that “ACKs receive LTS merges from upstream and bug fixes for Android-specific code.” These Android-specific fixes include the security patches the company lists in its monthly Android Security Bulletins. Starting with kernel 6.6, the support lifetime for the stable (LTS) kernels is four years. When kernels are no longer supported, devices running the relevant Android versions are considered “vulnerable” by Google.
Furthermore, Mountain View is simplifying the ACK release cycle. The company will now provide just a single new ACK branch for each kernel release, which is why Android 15 will exclusively use the android15-6.6 branch.