How Android works
The big picture
Draw Android's whole stack from memory, and see one tap cross every layer.
4 pages39 min4 interactive4700 words
- 01The layered stackAndroid is seven layers deep. Each one has its own language, its own process model and its own update story — and each boundary between them is an interface someone deliberately designed.beginner11 mininteractive
- 02Processes and UIDs: an app is a Linux userThe single decision that makes Android's security model work: every app gets its own Linux user identity, its own process, and its own sandbox. Everything else follows from that.beginner10 mininteractive
- 03What happens when you tap an iconThe whole platform, in thirty seconds. A tap on the launcher becomes a process, a window, a frame and a photon — and every module on this site is one line of this story.beginner10 mininteractive
- 04AOSP vs GMS vs OEM: why Android is four products"Android" names at least four different things — an open-source project, a Google app suite, a vendor stack and a shipping phone. Confusing them explains most of the platform's politics and half its bugs.beginner8 mininteractive
Test yourself
Test yourself: The big picture
What is AOSP?