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Johan Lorenzo de759bb336
Bug 1612540 - part 1: Move Fennec Beta to GitHub releases and a to a dedicated hook (#8270)
2 years ago
.github For #5909: Updates docs for improved accessibility process 2 years ago
app UITests: New tests for save Login prompt (#8381) 2 years ago
automation 3088 filter incomplete locales on release builds (#7581) 2 years ago
buildSrc For #8504 - Update Lottie version to 3.3.0 2 years ago
certificates Adds certificates to repository 2 years ago
config No Issue: Add custom detekt rule to blacklist certain properties 2 years ago
docs For #4807 - Always navigate to settings after deleting data 2 years ago
fastlane Adding l10n screenshot tests for Fenix (#3562) 2 years ago
gradle/wrapper For #7483: upgrade gradle to v5.6.4. 2 years ago
mozilla-detekt-rules For #7698: Adds search back button animation (#7840) 2 years ago
taskcluster Bug 1612540 - part 1: Move Fennec Beta to GitHub releases and a to a dedicated hook (#8270) 2 years ago
.adjust_token Fixes #675: Integrate Adjust SDK (for Greenfield flavor) 3 years ago
.cron.yml Bug 1608882 - part 1: Move Fennec Nightly to a dedicated hook 2 years ago
.editorconfig For #4326 - Updates codebase to support latest version of ktlint 2 years ago
.gitattributes Adds a gitattribute file to manage changelog merges 2 years ago
.gitignore For #3869 - Uses RegionSearchLocalizationProvider in the search engine provider 2 years ago
.taskcluster.yml Bug 1610725 - Support Action Tasks in CoT for Fenix. r=jlorenzo 2 years ago Add Mozilla Code of Conduct file 3 years ago
Gemfile Adding l10n screenshot tests for Fenix (#3562) 2 years ago
Jenkinsfile For #6208 - Sync Int Tests fix path for showing the html report file (#6209) 2 years ago
LICENSE Fixes #163: Add LICENSE 3 years ago Fixes #7895 - Update chat link (#7897) 2 years ago
build.gradle No Issue: Add custom detekt rule to blacklist certain properties 2 years ago
codecov.yml No issue: Add threshold to codecov (#4751) 2 years ago Configure either geckoview beta or nightly at compile-time (#4851) 2 years ago
gradlew For #7483: upgrade gradle to v5.6.4. 2 years ago
gradlew.bat For #7483: upgrade gradle to v5.6.4. 2 years ago
l10n.toml Import l10n. 2 years ago
settings.gradle No Issue: Add custom detekt rule to blacklist certain properties 2 years ago
version.txt Bug 1612540 - part 1: Move Fennec Beta to GitHub releases and a to a dedicated hook (#8270) 2 years ago

Firefox Preview

Task Status codecov

Firefox Preview (internal code name: "Fenix") is an all-new browser for Android, based on GeckoView and Mozilla Android Components.

** Note: The team is currently experiencing heavy triage and review load, so when triaging issues, we will mainly be looking to identify S1 (high severity) issues. See our triage process here. Please be patient if you don't hear back from us immediately on your issue! **

I want to open a Pull Request!

We encourage you to participate in this open source project. We love Pull Requests, Bug Reports, ideas, (security) code reviews or any other kind of positive contribution.

Since we are a small team, however, we do not have the bandwidth to review unsolicited PRs. Please follow our Pull Request guidelines, or we may close the PR.

To make it easier to review, we have these PR requirements:

  • Every PR must have exactly one issue associated with it.
  • Write a clear explanation of what the code is doing when opening the pull request, and optionally add comments to the PR.
  • Make sure there are tests - or ask for help on how the code should be tested in the Issue!
  • Keep PRs small and to the point. For extra code-health changes, either file a separate issue, or make it a separate PR that can be easily reviewed.
  • Use micro-commits. This makes it easier and faster to review.
  • Add a screenshot for UX changes (this is part of the PR checklist)

As a small team, we have to prioritize our work, and reviewing PRs takes time. We receive lots of PRs every day, so if you can keep your PRs small, it helps our small team review and merge code faster, minimizing stale code.

Keep in mind that the team is very overloaded, so PRs sometimes wait for a very long time. However this is not for lack of interest, but because we find ourselves in a constant need to prioritize certain issues/PRs over others. If you think your issue/PR is very important, try to popularize it by getting other users to comment and share their point of view.

Getting Involved

Before you attempt to make a contribution please read the Community Participation Guidelines.

Beginners! - Watch out for Issues with the "Good First Issue" label. These are easy bugs that have been left for first timers to have a go, get involved and make a positive contribution to the project!

Build Instructions

Note: Both Android SDK and NDK are required.

  1. Clone or Download the repository:
git clone
  1. Import the project into Android Studio or build on the command line:
./gradlew clean app:assembleGeckoBetaDebug

Use app:assembleGeckoNightlyDebug to build with the Gecko Nightly version instead.

  1. Make sure to select the correct build variant in Android Studio. See the next section.

Guide to Build Variants

We have a lot of build variants. Each variant is composed of two flavors. One flavor is the version of Gecko to use and the other describes which app id and settings to use. Here is a description of what each means:

  • geckoBeta (recommended) uses the Beta variant of the Gecko rendering engine, which corresponds to the next version of Gecko which will go to production
  • geckoNightly uses the Nightly variant of the Gecko rendering engine, which is the version which will arrive after beta and is less stable

  • debug uses debug symbols and debug signing, adds tools like LeakCanary for troubleshooting, and does not strip unused or wasteful code
  • fenixNightly is a release build with nightly signing which uses the org.mozilla.fenix.nightly app id for nightly releases to Google Play
  • fenixBeta is a release build with beta signing which uses the org.mozilla.fenix.beta app id for beta releases to Google Play
  • fenixProduction is a release build with release signing which uses the org.mozilla.fenix app id for production releases to Google Play
  • fennecProduction is an experimental build with release signing which uses the org.mozilla.firefox app id and supports upgrading the older Firefox. WARNING Pre-production versions of this may result in data loss.
  • forPerformanceTest: see "Performance Build Variants" below.

Performance Build Variants

For accurate performance measurements, read this section!

If you want to analyze performance during local development (note: there is a non-trivial performance impact - see caveats):

  • Recommendation: use a forPerformanceTest variant with local Leanplum, Adjust, & Sentry API tokens: contact the front-end perf group for access to them
  • Rationale: forPerformanceTest is a release variant with debuggable set to true. There are numerous performance-impacting differences between debug and release variants so we need a release variant. To profile, we also need debuggable, which is disabled on other release variants. If API tokens are not provided, the SDKs may change their behavior in non-trivial ways.
  • Caveats:
    • debuggable has a non-trivial & variable impact on performance but is needed to take profiles.
    • Random experiment opt-in & feature flags may impact performance (see perf-frontend-issues#45 for mitigation).
    • This is slower to build than debug builds because it does additional tasks (e.g. minification) similar to other release builds

Nightly forPerformanceTest variants with API tokens already added are also available from Taskcluster.

If you want to run performance tests/benchmarks in automation or locally:

  • Recommendation: production builds. If debuggable is required, use recommendation above but note the caveat above. If your needs are not met, please contact the front-end perf group to identify a new solution.
  • Rationale: like the rationale above, we need release variants so the choice is based on the debuggable flag.

For additional context on these recommendations, see the perf build variant analysis.

You will need to sign forPerformanceTest variants. For local development, our recommendation is to add the following configuration to app/build.gradle:

android { // this line already exists
    // ...

    buildTypes { // this line already exists
        // ...

        forPerformanceTest releaseTemplate >> { // this line already exists.
            // ...

            signingConfig signingConfigs.debug

This recommendation will let you use AS just like you do with debug builds but please do not check in these changes.

See perf-frontend-issues#44 for efforts to make performance signing easier.

Pre-push hooks

To reduce review turn-around time, we'd like all pushes to run tests locally. We'd recommend you use our provided pre-push hook in config/ Using this hook will guarantee your hook gets updated as the repository changes. This hook tries to run as much as possible without taking too much time.

To add it on Mac/Linux, run this command from the project root:

ln -s ../../config/ .git/hooks/pre-push

or for Windows run this command using the Command Prompt with administrative privileges:

mklink .git\hooks\pre-push ..\..\config\

or using PowerShell:

New-Item -ItemType SymbolicLink -Path .git\hooks\pre-push -Value (Resolve-Path config\

To push without running the pre-push hook (e.g. doc updates):

git push <remote> --no-verify helpers

There are multiple helper flags available via that will help speed up local development workflow when working across multiple layers of the dependency stack - specifically, with android-components, geckoview or application-services.

android-components auto-publication workflow

Specify a relative path to your local android-components checkout via

If enabled, during a Fenix build android-components will be compiled and locally published if it has been modified, and published versions of android-components modules will be automatically used instead of whatever is declared in Dependencies.kt.

application-services composite builds

Specify a relative path to your local application-services checkout via substitutions.application-services.dir.

If enabled, a multi-project gradle build will be configured, and any application-services dependency will be substituted for the local version. Any changes to application-services will be automatically included in Fenix builds.


Specify a relative path to your local mozilla-central checkout via dependencySubstitutions.geckoviewTopsrcdir, and optional a path to m-c object directory via dependencySubstitutions.geckoviewTopobjdir.

If these are configured, local builds of GeckoView will be used instead of what's configured in Dependencies.kt. For more details, see


This Source Code Form is subject to the terms of the Mozilla Public
License, v. 2.0. If a copy of the MPL was not distributed with this
file, You can obtain one at