AOSP Internals

A Developer's Guide to the Android Open Source Project

A comprehensive technical book covering the full AOSP stack — from kernel to apps — with every claim referencing real source code file paths and line numbers.

Read online: https://aospbooks.github.io/aosp-internal-book/

Using AI? Point your assistant at https://aospbooks.github.io/aosp-internal-book/llms.txt — an llmstxt.org-style index that lets the model find the right chapter for any AOSP subsystem without crawling the whole site.

If you spot errors, missing details, or have suggestions, please open an issue or submit a pull request — feedback from AOSP developers and enthusiasts is very welcome.

What This Book Covers

67 chapters organized bottom-to-top through the Android architecture:

Part	Ch.	Topics
Front	0	Frontmatter
I	1	Introduction
I	2	Source Code & Build System (Soong/Bazel/Kleaf)
I	3	Feature Flags (aconfig)
II	4	Boot and Init
II	5	Kernel (GKI)
II	6	System Properties
III	7	Bionic & Linker
III	8	Memory Management
III	9	Binder IPC
III	10	HAL (HIDL/AIDL)
III	11	NDK
IV	12	Native Services
IV	13	Graphics & Render Pipeline (OpenGL ES/Vulkan/Skia/HWUI)
IV	14	Animation System
IV	15	Audio System (Spatial)
IV	16	Media & Camera
IV	17	Sensors
V	18	ART Runtime
V	19	Native Bridge (Berberis)
VI	20	system_server
VI	21	Intent System
VI	22	Activity & Window Management
VI	23	Window System
VI	24	Display System
VI	25	View System
VII	26	Package Manager
VII	27	Content Providers
VII	28	Notifications
VII	29	Power Management
VII	30	Background Tasks
VII	31	Multi-User
VII	32	Account & Sync
VII	33	Location
VII	34	Storage
VIII	35	Networking (VCN/Thread)
VIII	36	Telephony (IMS)
VIII	37	Bluetooth
VIII	38	NFC
VIII	39	USB & ADB
IX	40	Security (TEE/Trusty)
IX	41	Credential Manager
IX	42	DRM
IX	43	LFI In-Process Sandbox
X	44	Widgets & RemoteViews (RemoteCompose)
X	45	WebView
X	46	Accessibility
X	47	Internationalization
XI	48	SystemUI (Monet/Keyguard)
XI	49	Launcher3
XI	50	Settings
XII	51	AI & AppFunctions (Computer Control)
XII	52	Companion & Virtual Devices
XII	53	NPU Manager
XIII	54	Mainline Modules (APEX)
XIII	55	OTA Updates
XIII	56	Virtualization (pKVM/crosvm)
XIII	57	Testing (CTS/VTS/Ravenwood)
XIII	58	Debugging Tools (Perfetto)
XIV	59	Architecture Support (ARM/x86/RISC-V)
XIV	60	Emulator
XIV	61	Device Policy
XIV	62	Device Form Factors
XIV	63	Print Services
XIV	64	Camera2 Pipeline
XV	65	Custom ROM Guide (step-by-step)
XV	66	Running Windows Games on Android
App.	A	Key Files Reference
App.	B	Glossary
App.	C	Why Kotlin Isn't on the Public API
App.	D	Android 17 Updates

How to Give Feedback

• Found an error? Open an issue describing the chapter, section, and what's wrong.
• Have a suggestion? Pull requests are welcome — even small fixes like typos or broken source paths.
• Know a topic deeply? We especially value feedback from engineers who work on specific AOSP subsystems.

Quick Start

Docker

./serve.sh           # start (http://localhost:8000)
./serve.sh off       # stop
./serve.sh status    # check if running
./serve.sh pdf       # build PDF → site/aosp-internals.pdf
./serve.sh epub      # build EPUB → site/aosp-internals.epub

The pdf command stops any running server, then builds all 67 chapters into a single PDF with rendered Mermaid diagrams (takes a while — uses Playwright/Chromium).

The epub command works the same way, producing an EPUB3 file with rendered Mermaid diagrams suitable for Apple Books, Google Play Books, and other readers.

Without Docker

# Install (one-time)
pip install properdocs mkdocs-material pymdown-extensions

# Create symlinks (one-time)
mkdir -p docs
for f in [0-9]*.md [A-Z]-*.md index.md; do ln -sf "../$f" "docs/$f"; done

# Start
properdocs serve                   # http://127.0.0.1:8000

# Build static site
properdocs build                   # output in site/

Open http://localhost:8000 — chapters in the sidebar, Mermaid renders live, hot-reload on edits.

AOSP Manifest Snapshots

A companion tool captures point-in-time, fully-pinned repo manifest snapshots of the AOSP source tree and diffs two of them into four branch-named files: a Markdown navigator, a kernel-changelog of per-repository commits, an added/removed-projects file with full history, and an LLM analysis prompt. Shallow (clone-depth) and ignore-globbed projects are skipped. Useful for "what changed between two AOSP releases."

# Take a snapshot (resolves every <project> to a HEAD SHA, prompts for label/notes)
python3 tools/manifest_snapshot.py snap --aosp-root /path/to/aosp

# Compare two snapshots → manifest-snapshots/_compare/<oldrev>-to-<newrev>/{report.md,changes.txt,added-removed.txt,analysis-prompt.txt}
python3 tools/manifest_snapshot.py compare \
    manifest-snapshots/<branch>/<date-A> \
    manifest-snapshots/<branch>/<date-B> \
    --aosp-root /path/to/aosp

The tool is read-only against .repo/ — it never writes inside the AOSP checkout. See manifest-snapshots/README.md for the full guide, flag reference, and the read-only guarantee.

GitHub Actions

Tests properdocs build on push to main and PRs (~2 min).

Project Structure

[0-9]*.md                  67 chapter files
[A-D]-appendix-*.md        4 appendix files
index.md                   Website homepage
properdocs.yml             ProperDocs config (Material theme + Mermaid)
docs/                      Symlinks for ProperDocs (gitignored)
mkdocs-mermaid-renderer/   Shared Mermaid SVG renderer (Playwright + cache)
mkdocs-pdf-generate/       MkDocs plugin: PDF export
mkdocs-epub-generate/      MkDocs plugin: EPUB export
Dockerfile                 python:3.12-slim + Playwright + ProperDocs plugins
docker-compose.yml         serve / build-site / build-pdf / build-epub
tools/                     Helper scripts (manifest_snapshot.py + tests)
manifest-snapshots/        Pinned AOSP manifests by branch/date + comparison reports
CLAUDE.md                  Project rules for AI agents
.claude/skills/            book-writer
.github/workflows/         CI: properdocs build test

License

This project is licensed under the Apache License 2.0, matching the license of the Android Open Source Project it analyzes.