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This is an effort to produce an AOSP based Android ROM with only the minimum binary blobs in order for all hardware to function.

Additionally, we seek to produce signed deterministic builds allowing for high accountability via redundant CI systems all getting the same hash.

Heavily inspired by the former CopperheadOS (RIP) project. We seek to provide a trustable path to free public AOSP builds patched for privacy and security.

Additionally, this build system is intended to make it easy to build, sign and publish your own custom AOSP rom from patches/configs/branding as you see fit.

A common build system/strategy for vanilla AOSP and AOSP forks also makes it easy to change between them as you see fit while still controlling your own keys making debugging and comparisons easier.


Public releases are pending sustainable/automated CI/CD work to do reproducible builds and multisig.

Testing is currently manual. "True" implies only all hardware and surface level functionality appears to work. E2E testing integration is WIP

Testers, builders, and hosting bandwidth needed.


Please join us on IRC: ircs://!os



  • 100% Open Source and auditable
    • Except for mandatory vendor blobs hash verified from Google Servers
  • Minimal changes to stock AOSP functionality
  • Automated build system:
    • Completely run inside Docker for portability
    • Customize builds from central config file.
    • Automatically pin hashes from upstreams for reproducibility
    • Automated patching/inclusion of upstream Android Sources
  • Removed:
    • Google Play Services
    • Proprietary system apps
    • OMA-DM backdoors
    • Browser2 - Mostly unmaintained
    • Webview - Mostly unmaintained
    • Calendar - Mostly unmaintained
    • Quicksearch - Requires Google Play Services. Also removed from Launcher.
  • Added:
    • Custom Android Verified Boot included in factory images
    • F-Droid - Trusted as system app without need to enable "Unknown Sources"
    • Chromium - With several privacy/security patches
    • Backup - Minor OS changes made to allow backing up any app
    • Updater - Patched to use update server


  • Reproducible builds
    • Allow third parties to prove a build came from expected open source code.
  • Verified Builds
    • Test builds signed with test keys are automated and used for verification.
    • Third party verifiers will maintain webhook activated build nodes
      • Will be in different legal jurisdictions
      • should have a public reputation to lose if they tamper a build
      • can offer mirrors signed with their own keys
      • will publish signatures for test builds to be in 'verified' channel
    • Updater app will verify signatures from m-of-n builders (e.g 2 of 3)
    • Ability to build/sign/update own releases via Terraform automation
  • Compatibility Test Suite
    • Every device should have a sponsor with an automated CTS test station
  • Hardening
    • Test and integrate GrapheneOS patches in dedicated release channel
      • Hardened Memory Allocator
      • Chromium security/privacy patches
      • Various platform patches for better permissions controls
    • BadUSB
      • Setup global settings option to toggle USB OTG support
      • Disable all USB devices by default
    • Allow build options to disable hardware as needed for airgap setups.
  • Remote Attestation
    • Auditor app integration
  • Two Factor Authentication
    • Replace proprietary Google Play Services U2F with open/auditable one.
  • Accessibility
    • Global Dark Mode
    • One Handed Mode
  • Fluff
    • Wallpaper/boot animation
    • Support channel link on home screen
    • Support flashing from windows for confused people we take pity on


Device Codename Tested Verifiable Secure Boot Download
Pixel 3a XL Bonito FALSE FALSE AVB 2.0 Soon™
Pixel 3a Sargo FALSE FALSE AVB 2.0 Soon™
Pixel 3 XL Crosshatch TRUE FALSE AVB 2.0 Soon™
Pixel 3 Blueline TRUE FALSE AVB 2.0 Soon™
Pixel 2 XL Taimen TRUE FALSE AVB 1.0 Soon™
Pixel 2 Walleye FALSE FALSE AVB 1.0 Soon™
Pixel XL Marlin FALSE FALSE dm-verity Soon™
Pixel Sailfish FALSE FALSE dm-verity Soon™

Release hosting is sponsored by JFrog




  1. Go to "Settings > About Phone"
  2. Tap "Build number" 7 times.
  3. Go to "Settings > System > Advanced > Developer options"
  4. Enable "USB Debugging"
  5. Connect to device to laptop via short USB C cable
  6. Hit "OK" on "Allow USB Debugging?" prompt on device if present.
  7. Verify ADB connectivity
adb devices

Note: Should return something like: "7CKY1QD3F device"


  1. Extract
cd crosshatch-PQ1A.181205.006
  1. Connect
  2. Go to "Settings > System > Advanced > Developer options"
  3. Enable "OEM Unlocking"
  4. Unlock the bootloader via ADB
adb reboot bootloader
fastboot flashing unlock

Note: You must manually accept prompt on device.

  1. Flash new factory images


  1. Connect
  2. Lock the bootloader
adb reboot bootloader
fastboot flashing lock
  1. Go to "Settings > About Phone"
  2. Tap "Build number" 7 times.
  3. Go to "Settings > System > Advanced > Developer options"
  4. Disable "OEM unlocking"
  5. Reboot
  6. Verify boot message: "Your device is loading a different operating system"
  7. Go to "Settings > System > Advanced > Developer options"
  8. Verify "OEM unlocking" is still disabled


  • Failure to run these hardening steps means -anyone- can flash your device.
  • Past this point if signing keys are lost, all devices are bricked. Backup!


  1. Go to "Settings > System > Developer options" and enable "USB Debugging"
  2. Reboot to recovery
adb reboot recovery
  1. Select "Apply Update from ADB"
  2. Apply Update
adb sideload
  1. Go to "Settings > System > Developer options" and disable "USB Debugging"



  • Linux host system
  • Docker
  • x86_64 CPU
  • 10GB+ available memory
  • 350GB+ free disk space

Generate Signing Keys

Each device needs its own set of keys:

make DEVICE=crosshatch keys

Build Factory Image

Build flashable images for desired device:

make DEVICE=crosshatch clean build release



Do basic cleaning without deleting cached artifacts/sources:

make clean

Clean everything but keys

make mrproper


Build a given device twice from scratch and compare with diffoscope:

make compare


Create a shell inside the docker environment:

make shell


Output all untracked changes in android sources to a patchfile:

make diff > patches/my-feature.patch


  1. Update to latest upstream sources.
make config
  1. Build all targets impacted by given change
make DEVICE=crosshatch release
  1. Commit changes to a PR
  2. Author or reviewer manually tests and documents in CHANGELOG
  3. Reviewer security audits local/upstream changes and documents in CHANGELOG
  4. Maintainer does signed merge of changes to master
  5. Maintainer makes signed release tag. (E.g: "9.0.1_r37-hb37")


If you'd like to manage you own OTAs with your own signing keys, you can make the following changes:

  1. Update patches/platform/add-updater.patch and change to whatever server you'll be placing these images.
  2. make DEVICE=<device-name> OTA_CHANNEL=stable build release a. OTA_CHANNEL will default to beta
  3. Upload files from build/release/* to your server.
  4. Your server should be configured to have wherever you OTAs are being shipped to as part of the root directory. SSL is highly recommended.


  • Release process does not yet include OTA updates or binary hosting.
  • Volunteers needed! Join #!os on to help.


Who is this project for?

Individuals that desire a device that favors privacy and security over easy access to proprietary software and services.

Wait can I not run -Insert-App-Here-

You technically can download/install most apps in the Play store but we of course can't recommend that. Some apps that have a hard requirement on Google Play Services can be tricked with [MicroG][mg] but this increases attack surface and though it will probably work in many cases, this is not supported or recommended.

Yalp store is an open source browser for Google Play Store and is available on F-Droid.

Also see "Alternatives" below to find alternatives for popular apps.

Why is -Insert-Device-Here- not supported?

Most vendors don't release sources and tooling to reproduce their builds or do so with substantial delays. Many vendors even disable critical security features they don't understand and allow various Supply Chain Attacks. These are a headache to reverse engineer, test, audit, patch, and generally maintain.

Unless a vendor decides to produce source repos with at least the quality of AOSP we will only support AOSP supported devices which today means the Pixel series of mobile handsets.

Pixel devices start at $100-200 and we will try to maintain support for at least one device at this price point to keep the project accessible.

Why not use LineageOS, AOKP, or insert-project-here?

As of the time of this writing most popular ROMs are virtually unusable without Google Play Services and the proprietary parts of android. They also tend to make changes that make taking upstream source code time consuming thus often delaying security updates.

Secondly virtually all roms sign using "test" keys, leaving all of them vulnerable to Evil Maid Attacks and thus worse-off security wise than stock Android.

Third, builds are almost never easily reproducible if at all meaning that a single coerced maintainer could slip in a subtle flaw without very little chance of detection

Lastly, they almost all source binaries from sketchy locations like the infamous "TheMuppets" repo which an unknown number of people have push access to. This sort of activity acts as a security SPOF for popular roms.

Why should anyone trust this project?

Trust, but Verify. While we may be upstanding people today, we might be coerced tomorrow by a state actor that wants access to the device in your pocket. You can run our reproducible build systems yourself and sound the alarm if the builds we produce don't line up with the published source code.

The more people that verify, the less reason a bad actor has to try to attack maintainers. Maintaining a system that requires zero trust on the maintainers is a core part of our plan to be resistant to Australia-style strongarm backdoor requests.


Giving up Google Play services and stock proprietary applications is a big ask for a lot of people that have grown to rely on particular apps for their lifestyle.

To address this consider looking at some of the below alternatives for popular applications.

Some things won't have alternatives and in those cases you will have to decide to sideload a specific proprietary APK via Yalp Store or live without that app.

You may also find popular travel apps like Kayak, Uber ans Lyft have very usable mobile webapps you can pin to your desktop for a similar experience to a native app.

App Alternative(s) Notes
Chrome Chromium, OrFox Chromium is built-in to #!os
Play F-Droid, Yalp F-Droid is built-in to #!oa
GMail K9Mail
Drive Nextcloud
Music D-Sub Will need a Subsonic capable server
Maps OsmAnd~
Auth. Yubico Auth.
Hangouts Weechat,
Voice Ring
Youtube NewPipe, SkyTube


Use at your own risk. You might be eaten by a grue.