Simple Firefox for Android build

For additional, more detailed information, see the Firefox for Android wiki and the general Firefox build documentation.

uname -m

This section lists the hardware requirements for buiding Fennec:

• A decent speed CPU. While you can build Firefox on older hardware, it can take quite a bit of time to compile on slower machines. Having at least 8GB of RAM is recommended. If you have older hardware, it is strongly recommended that you use artifact mode.
• Fast broadband internet is strongly recommended as well. Both the development environment, and the source code repository, are quite large. Artifact mode regularly downloads large (50MB) binary archives.
• You must have a 64-bit operating system. As of early 2015 it is no longer possible to build Firefox on most 32-bit machines.
• If you're going to install Firefox for Android on a physical Android device, you'll need one running Android Ice Cream Sandwich (API 15) or later.
• You can also develop against an emulator; see MozillaWiki for more details. All the mach commands discussed on this page should work with an emulated Android device the same as on physical hardware.

Bootstrap dependencies

Run either of the following in a terminal.  You'll need Python version 2.7 or later, and curl or wget.  If you have curl installed (note that Mac OS X ships curl by default), run this command in your terminal:

curl -O https://hg.mozilla.org/mozilla-central/raw-file/default/python/mozboot/bin/bootstrap.py && python bootstrap.py

Or, if you have wget installed, run this instead:

wget -q https://hg.mozilla.org/mozilla-central/raw-file/default/python/mozboot/bin/bootstrap.py && python bootstrap.py

Choose 3. Firefox for Android Artifact Mode when prompted. 

The bootstrapping script will install system packages, the Android SDK (and NDK, if required), and the currently required versions of the Android platform plus extras. If you want to know more about what Bootstrap.py is doing you can look at our detailed setup instructions. Please follow the steps in the termnial to complete the configuration. If you want to use git, when you are aksed to run the Mercurial configuration wizard, you can select option 2. No.

The bootstrap script will print out configuration options for you when it finishes (more on this below).  For now, copy this configuration text to a safe place and continue on.  You can re-run the bootstrap script to print this information again later.

Once you have all the dependencies installed, you need to clone the Firefox repository.

Get the source

Get the latest source code from Mozilla's Mercurial code repository. This may take a while; it's a lot of code!  We recommend that you add the progress extension to your Mercurial configuration.  This will provide feedback during the lengthy clone process.  See the documentation explaining how to enable the Mercurial progress extension.

hg clone https://hg.mozilla.org/mozilla-central

If you are using a slow or unreliable internet connection, hg clone might fail if it gets interrupted. In that case, you are strongly encouraged to download a Mercurial bundle file instead of waiting for hg clone.

Choose what parts of Firefox for Android you want to modify

Firefox for Android is built in two layers.  The Firefox for Android “front-end” — which includes the home panels, UI for settings, menus, etc., Firefox Sync, and most data storage — is implemented using Java, the Android Platform SDK, JavaScript, HTML, and CSS.  Firefox for Android is built on top of the Gecko platform back-end. Gecko is Mozilla's web rendering engine, similar to Edge, Blink, and WebKit, and is responsible for rendering web content, running JavaScript code, and providing web APIs to pages. Gecko is implemented using C++ and JavaScript.

Here is a table summarizing the pros and cons of working on the different parts.

Do you want to modify just Firefox for Android, or do you want to modify the Gecko platform?

• I want to work on the front-end: the look and feel of Firefox for Android.
• I want to work on the back-end: Web APIs, HTML rendering or other parts of the Gecko platform.

Prepare a Firefox for Android mozconfig file

The build scripts will read from the mozconfig file in your source directory (where you cloned the mozilla-central source repository into) to determine what kind of build to produce, although you can configure this if you need to.  You must use $HOME instead of ~ in your mozconfig because ~ does not get expanded.

By default, the build system creates a build of Firefox for Android roughly equivalent to the official Firefox for Android Nightly builds. If that's not exactly what you want, there are many build configuration options to choose from. It's strongly recommended that you only use options that you fully understand. Although you may already have your own Android path setup, we strongly recommended you use the version come with above steps (bootstrap.py) . This is will prevent Fennec from interfering with your original development environment.

I want to work on the front-end

Firefox for Android supports a fast build mode called artifact mode.  (Some mobile team managers call it manager mode since it's particularly helpful if you only write code infrequently.)  Artifact mode downloads pre-built C++ components rather than building them locally, trading bandwidth for time.

To use artifact mode, paste the following into your mozconfig file:

# Build Firefox for Android:
ac_add_options --enable-application=mobile/android
ac_add_options --target=arm-linux-androideabi
# With the following Android SDK:
ac_add_options --with-android-sdk="/absolute/path/to/android-sdk"
# Enable artifact building:
ac_add_options --enable-artifact-builds
# Write build artifacts to:
mk_add_options MOZ_OBJDIR=./objdir-frontend

You should be ready to build with artifact mode!

I want to work on the back-end

Paste the following into your mozconfig file:

# Build Firefox for Android:
ac_add_options --enable-application=mobile/android
ac_add_options --target=arm-linux-androideabi
# With the following Android SDK and NDK:
ac_add_options --with-android-sdk="/absolute/path/to/android-sdk"
ac_add_options --with-android-ndk="/absolute/path/to/android-ndk-r11c" 
# Write build artifacts to:
mk_add_options MOZ_OBJDIR=./objdir-droid

Ensure that the Android NDK you've specified (r11c in the example above) matches what you have installed locally.

If you're planning on hacking the C/C++ code, you probably want to create a debug build instead of a release build.  Add the following lines to your mozconfig:

ac_add_options --enable-debug
ac_add_options --enable-debug-symbols

Configuration options

I want to build an x86 version of Firefox for Android

Version 23 and later Android x86 emulators with hardware acceleration are fast enough for local development.  They're an attractive alternative if you have recent hardware and an old Android device (or no Android device).  Both artifact mode and regular mode support building APKs for x86 architectures.  Just replace the line ac_add_options --target=arm-linux-androideabi with:

ac_add_options --target=i386-linux-android

(You probably want to change the MOZ_OBJDIR directory, too.)  Now when you build, you should produce an x86 version of Firefox for Android!

For more configuration options, see the general Firefox documentation on configuring build options.

Deploy Firefox to an Android device

Quick start

The bare minimum: run these commands to build, package, install, and run a fresh Firefox for Android on your Android device.

./mach build
./mach package
./mach install
./mach run

Build

Enter the mozilla-central subdirectory (created by the hg clone command).

To build Firefox for Android (compile and link all C/C++, Java, and JavaScript source code), run:

./mach build

Building can take a significant amount of time, depending on your hardware, OS, and chosen build options. Linux builds on a fast box may take under 15 minutes, but builds on a slow machine may take several hours. If you're using artifact mode, builds should take less than five minutes. See tips for making builds faster.

Rebuild

To build after making changes, run:

./mach build

This will only rebuild what is necessary for these changes. It is also possible to use:

./mach build mobile/android

This will build any altered Firefox for Android front-end code. If you are using artifact mode, this should always work. If you are building the Gecko back-end, this may yield incorrect results, so it is not recommended.

Package

Running an Android application on a device is a little more involved than running a Desktop Firefox binary.  First, we need to package everything into an Android package.  To produce an APK, run:

./mach package

The produced APK file can be found in your $OBJDIR/dist folder, and will be called something like fennec-56.0a1.en-US.android-arm.apk.

Install and run

To install the Android package to your device and launch it, connect your Android device and enable USB debugging, and then run the following:

./mach install
./mach run

The name of the App that appears on your Android device will be "Fennec $USER", where $USER is the username under which you built the code.

Now the fun starts

You’re ready to start hacking. You have the code, you’ve compiled Firefox, and it’s running on your phone. The next steps are up to you: join us on IRC in #introduction and find yourself a bug to work on!

Thank you

Mozilla's strength is the community behind it; Firefox is the product of a global development team working to keep the Web free, open and participatory, and your contributions will make Firefox and the Web better for hundreds of millions of people around the world.

Developing Firefox for Android in Android Studio

The Firefox for Android front-end team develop the product in Android Studio. There is a Gradle build configuration, parallel to the mach build configuration.  Eventually, we intend to use Gradle in the mach build configuration.

The Gradle configuration is now "in the source directory".  To verify that everything is working, ensure that you've built and packaged successfully, and then run:

./mach gradle clean app:assembleLocalOldAustralisDebug

Next, simply import the top source directory (mozilla-central, as produced by hg clone) into Android Studio.  You should now have a shiny new Gradle-based project in Android Studio! Try it out by choosing Build > Rebuild project.

It should look something like:

Setting the Run/Debug Configuration and Build Variant

The Gradle build configuration may contain more than one Gradle module, which can define many Run/Debug Configurations.  You want the "app" Run Configuration:

See the documentation for more.

The configuration also defines multiple Product Flavors, which contribute to Build Variants.  You want one of the following combinations, depending on the version of your test device:

See the Google build documentation for more.

Things that are supported in the IDE

• Running, debugging, and profiling Firefox for Android in the IDE.  The app project defines the Android Application.
• Editing Java source code under mobile/android.  Modifications to any of the Java code should prompt a fresh build and install.
• Editing Android resources under mobile/android, including in mobile/android/base/resources.  In many cases the Android Layout Editor is fully functional.
• Modifying the Android string definitions in mobile/android/base/strings.xml.in and mobile/android/base/locales/en-US/*.dtd.  Modifications should be picked up at the next build; they may not be noticed automatically.  (This is because the Android strings.xml file is generated, and the generation only happens in response to a build.)
• Editing "omnijar" JavaScript source code under mobile/android, including in mobile/android/content, mobile/android/components, and mobile/android/modules, and under toolkit/.  Modifications to JavaScript code should be picked up at the next build.  Such modifications should rebuild the omnijar and prompt a fresh build and install.
• Editing "omnijar" chrome XHTML, CSS, and JS resources under mobile/android, including in mobile/android/content, and under toolkit/.

Things that are not supported in the IDE

• Modifying build system configuration and definitions and modifying mobile/android/base/AndroidManifest.xml.in or the sub-manifests.  See bug 1221344 for an example of what can go wrong here.
• Modifying generated Java code such as mobile/android/base/java/org/mozilla/gecko/AppConstants.java.in.
• Modifying C++ source code anywhere in the tree.
• Modifying "omnijar" JavaScript source code outside of mobile/android.  (If you modify JavaScript outside of mobile/android, say under dom/, the changes will be recognized the next time "omnijar" files inside mobile/android are edited.)
• Running Robocop tests.  (Use mach robocop to run these tests locally.)
• Running mochitest-chrome tests.  (Use mach test to run these tests locally.)

Troubleshooting

• First, check if the Gradle configuration is working:

  ./mach gradle clean app:assembleLocalOldAustralisDebug

  That should complete successfully.

• Second, check that you're building the correct Gradle module and the correct build variant. If you see a runtime error like

  A/GeckoLoader: Couldn't load mozglue. Trying native library dir.
  A/GeckoLoader: Library doesn't exist when it should.
  

  then you are probably running the "automation" Build Variant.  See the documentation on Build Variants and the discussion in bug 1246055.

• Third, ensure that you can install the APK to your device:

  ./gradlew clean app:install{Local,LocalOld}Debug

  This should complete successfully, where you choose "Local" or "LocalOld" depending on your target device.  See the documentation on Build Variants.

• It's possible to confuse the IDE about the state of the source directory.  To recover, try the following:
  • Select the root project and refresh everything in the IDE.
  • Open the root build.gradle file. If the IDE warns that the Gradle configuration has changed, accept the offer to Sync now.
  • Refresh the Gradle model manually: select View > Tool Windows > Gradle and click the blue Sync button in the top left.  In Android Studio, there's an icon to do this in the main toolbar -- it's labeled Sync Project with Gradle Files.
  • Clear the IDE cache manually:  select File > Invalidate caches and then restart the IDE.  (This should never be necessary.)

Required Android SDK and NDK versions

The Fennec build system requires the following versions:

If your build fails because you're missing one of the Android or Google requirements, your first step should be to run mach bootstrap. If you don't want to run the bootstrapper, you can manually install by running the Android SDK manager: try mach android, or $ANDROID_SDK/tools/android.

bug 1207680 tracks listing these version requirements in one place in the source code.