What AOSP is
AOSP, short for the Android Open Source Project, is the publicly available source code of the Android operating system. It contains everything needed to build a basic, working version of Android: the system framework, a set of core apps, and the tools to compile it all. Google leads the project and first released Android's source code in 2008, and every Android phone, from flagship models to hobbyist custom ROMs, is built on this shared foundation.
What is included, and what is not
AOSP provides the core of Android, including the runtime that executes apps, the system settings, basic apps such as a launcher and a dialer, and Android's security model. What it does not include is Google Mobile Services, the proprietary bundle that contains the Google Play Store, Gmail, Google Maps, and Google Play Services. Phone makers must license that bundle separately from Google, which is why a phone running pure AOSP has no Play Store at all.
Open-source licensing
Most of AOSP is released under the Apache License 2.0, a permissive license that lets anyone use, modify, and distribute the code, including in commercial products, without having to publish their own changes. The Linux kernel at the heart of Android is the main exception, since it uses version 2 of the GPL, which requires changes to be shared. This permissive approach is a big reason so many companies chose Android for their devices.
How phone makers and ROMs use it
Manufacturers such as Samsung and Xiaomi take AOSP, add their own interface, apps, and hardware drivers, and license Google's services to create the software on their phones. Custom ROM projects such as LineageOS start from the same code, adapting it to run on specific devices and adding their own features. Amazon's Fire OS for tablets is another well-known example, built on AOSP but with Amazon's own app store in place of Google's.
How Google develops it
Google develops new versions of Android largely in private and publishes the source code to AOSP when a release is ready, rather than working in the open day by day. In recent years it has also published AOSP code less often, which adds extra work for the projects that build on it. Even so, AOSP remains the common starting point for the entire Android world, from the largest phone makers to independent developers.
The bottom line
AOSP is the open-source heart of Android: the freely available code that every Android device, custom ROM, and fork is built on. It gives anyone the ability to build and modify Android, while Google's own apps and services remain a separate, licensed layer on top. Understanding that split explains why some Android devices come with the Play Store and others, including many custom ROMs, ship without it.
Related on Skillo
See also: What is a custom ROM on Android? Explained, What is Linux and why it runs the world.
Sources
Published date reflects the original event date (2026-10-23). This article is original Skillo editorial written from the sources above; facts were verified in September 2026.
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