Android is an operating system for a wide array of devices with different form factors. The documentation and source code for Android is available to anyone as the Android Open Source Project (AOSP). You can use AOSP to create custom variants of the Android OS for your own devices.
AOSP is designed so that there's no central point of failure, where one industry player restricts or controls the innovations of another. Therefore, AOSP is a full, production-quality developer product with source code open for customization and porting.
This section of documentation helps new AOSP developers get started with the platform and to perform essential development tasks.
Required terms
Following is a list of terms and definitions used throughout the Getting Started documentation. You should study each definition before continuing further.
- Android app developer
Android app developers writes Android apps or applications that run on Android. There are two classification of app developers: first-party (1p) and third-party (3p) app developers.
- Android first-party app developer
- An Android app developer that has access to AOSP System APIs and writes privileged and device manufacturer apps.
- Android third-party app developer
- An Android app developer who solely uses Android's public SDK to create Android apps.
If you want to develop third-party apps for Android, refer to
developers.android.com. The information on
this website is solely for those working directly with AOSP.
- Android debug bridge (adb)
- A command-line tool (
adb) that allows your workstation communicate with a virtual, software-emulated, or physical device. - Android-compatible device
- A device that can run any third-party app written by third-party developers using the Android SDK and NDK. Android-compatible devices must adhere to the requirements of the Compatibility Definition Document (CDD) and pass the Compatibility Test Suite (CTS). Android-compatible devices are eligible to participate in the Android ecosystem which includes potential licensure of the Android Play Store, potential licensure the Google Mobile Services (GMS) suite of applications and APIs, and use of the Android trademark. Anyone is welcome to use the Android source code, but to be considered part of the Android ecosystem, a device must be Android-compatible. For further information on compatibility and CTS, see the Android Compatibility Program overview
- Compatibility Definition Document (CDD)
- A document that enumerates the software and hardware requirements for an Android-compatible device.
- Contributor
A person who makes contributions to the AOSP source code. Contributors can be employees of Google, employees from other companies, and individuals with no company affiliation. Every AOSP contributor uses the same tools, follows the same code review process, and is subject to the same coding style. You don't have to be a contributor to use AOSP; you can download AOSP, modify it for your own needs, and deploy it on a device without contributing code for others to use.
There are limits to the type of code contributions Google accepts. For example, you might want to contribute an alternative application API, such as a full C++-based environment. Google would decline that contribution because Android encourages applications to be run in the ART runtime. Similarly, Google doesn't accept contributions such as GPL or LGPL libraries that are incompatible with licensing goals.
If you are interested in contributing source code, contact Google prior to beginning work.
- Compatibility Test Suite (CTS)
A free, commercial-grade test suite, available for download as a binary or as source in AOSP. The CTS is a set of unit tests designed to be integrated into your daily workflow. CTS's intent is to reveal incompatibilities, and ensure that the software remains compatible throughout the development process.
- Cuttlefish
A configurable virtual Android-powered device that can run remotely, using third-party cloud offerings, such as Google Cloud Engine, and locally on Linux x86 machines.
- Developer
In the context of AOSP, a developer is anyone who works with AOSP in any way. The term "developer" is used to generically refer to the various people who might read this documentation, such as original equipment manufacturers (OEMs), handset makers, carriers, and System-on-a-Chip (SoC) creators.
- Google Mobile Services (GMS)
A collection of Google apps and APIs that can be pre-installed on devices.
- Target
A permutation of a device, such as a specific model or form factor. For example,
aosp_cf_x86_64_phone-userdebugrepresents a x86 65MB phone with debugging information that is designed to run on the cuttlefish emulator.
Governance philosophy
A group of companies known as the Open Handset Alliance (OHA), led by Google, originated Android. Today, many companies—both original members of the OHA and others—have invested heavily in Android. These companies have allocated significant engineering resources to improve Android and bring Android devices to market.
The companies that have invested in Android have done so because they believe an open platform is necessary. Android is intentionally and explicitly an open source effort (as opposed to free software); a group of organizations with shared needs has pooled resources to collaborate on a single implementation of a shared product. First and foremost, the Android philosophy is pragmatic. The objective is a shared product that each contributor can tailor and customize.
Of course, uncontrolled customization can lead to incompatible implementations. To prevent incompatibility, the Android Open Source Project (AOSP) maintains the Android Compatibility program, which spells out what it means to be Android-compatible and what's required of device builders to achieve that status. Anyone can use the Android source code for any purpose, and Google welcomes all legitimate uses. However, to take part in the shared ecosystem of applications OHA members are building around Android, device builders must participate in the Android Compatibility program.
AOSP is led by Google, who maintains and further develops Android. Although Android consists of multiple subprojects, AOSP is strictly project management. Google views and manage Android as a single, holistic software product, not a distribution, specification, or collection of replaceable parts. Google's intent is that device builders port Android to a device; they don't implement a specification or curate a distribution.
What's next?
If you're new to AOSP and want to run through a tutorial on AOSP development, proceed with AOSP tutorial.
If you believe that your device needs to be Android-compatible, refer to the Android Compatibility program.
If you want to learn about the background of AOSP, including Google's participation in the platform, see AOSP frequently asked questions.