Other meanings of Android Open Source Project
Open source software
The Android Open Source Project (AOSP) is the open-source, publicly accessible component of the Android mobile operating system, maintained by Google under the Apache License 2.01. It includes the core operating system, middleware, and key applications, but excludes Google's proprietary services such as Google Play and the Google Mobile Services suite2. AOSP serves as the foundation for both Google's official Android releases and for countless third-party custom ROMs and Android forks worldwide3.
The Android Open Source Project was launched by Google in November 2007, coinciding with the formation of the Open Handset Alliance, a consortium of 84 technology companies committed to open mobile standards. The first public source code release occurred in October 2008 with the Android 1.0 codebase1. AOSP is governed by the Apache License 2.0, which permits unrestricted modification and redistribution, subject to the license terms2. This licensing choice was deliberate to encourage adoption by device manufacturers and developers while allowing Google to offer proprietary enhancements separately. The project's code is hosted on the official AOSP Gerrit instance and mirrored on GitHub, with contributions managed through a rigorous code-review process3.
AOSP consists of several layers built on the Linux kernel. Above the kernel sits the Hardware Abstraction Layer (HAL), which provides standard interfaces to hardware vendors. The Android Runtime (ART) executes applications, replacing the earlier Dalvik virtual machine1. The platform includes libraries for graphics, audio, networking, and security, as well as the system server that manages core services. The project also ships a set of open-source applications such as the browser, calendar, and contacts app, but these are minimal compared to the proprietary Google equivalents2. AOSP tracks the latest Android version in a master branch, while stable releases are tagged (e.g., android-14.0.0_r1), enabling device manufacturers to build on a specific base3.
The AOSP development process is led by Google engineers but accepts contributions from the broader community through the Gerrit code review tool3. Major changes are discussed on the android-platform mailing lists and at the annual Google I/O conference. While Google owns the trademark and controls the upstream direction, forks such as LineageOS and GrapheneOS demonstrate the project's independence by creating alternative distributions without Google services4. The project also maintains a Compatibility Definition Document (CDD) and a set of Compatibility Test Suite (CTS) tests to ensure that devices claiming Android compatibility meet minimum standards. However, AOSP itself does not guarantee compatibility with Google Play apps, which rely on proprietary APIs.
Despite its name, AOSP is not a fully usable operating system for most users: it lacks Google's Play Services, which are essential for many apps and features such as push notifications and location services1. AOSP is also the basis for non-phone devices, including smart TVs (Android TV), automotive infotainment (Android Automotive OS), and wearables (Wear OS), though each platform has its own additional open-source components2. A lesser-known fact is that the AOSP source tree includes experimental projects like Android Things (for IoT) and the Android SDK for building custom system images. The project has also been a subject of controversy: in 2019, Huawei was forced to rely on AOSP alone after U.S. trade restrictions, highlighting the distinction between the open-source project and Google's ecosystem4. Additionally, many early Android versions (pre-4.0) were developed in a closed-source manner before being released to AOSP, contrary to the open-source ideal1.
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