Skip to content
Switch branches/tags


Failed to load latest commit information.
Latest commit message
Commit time

Firefox Application Services

Application Services (a-s) is collection of Rust Components that are used to enable Firefox applications to integrate with Firefox accounts, sync, experimentation, etc. Each component is built using a core of shared code written in Rust, wrapped with native language bindings for different platforms.


To contribute, please review the Mozilla Community Participation Guidelines and then visit our how to contribute guide.


Get in touch with other community members on Matrix, or through issues here on GitHub.


High-level docs

The Application Services Book contains high-level documentation about the code in this repository. It's built from the ./docs/ directory.

Package docs

We use rustdoc to document both the public API of the components and the various internal implementation details. View them on Once you have completed the build steps, you can view the docs by running:

cargo doc --no-deps --document-private-items --open


Building the Rust Components

  1. Clone or Download the repository:
  $ git clone # (or use the ssh link)
  $ cd application-services
  $ git submodule init
  $ git submodule update --recursive
  1. Follow these instructions to install your system-level dependencies
  2. Run the a-s Rust unit tests
cargo test

Consumer build, integration and testing

The application-services library primary consumers are Fenix (Firefox on Android) and Firefox iOS. Assure you are able to run integration tests (for Android and iOS if using MacOS) by following the instructions to build for Android and iOS integrations.

Android integration builds and helpful tools

Firefox for iOS integration

Firefox Desktop

Rust Components

./components/ contains the source for each component, and its FFI bindings.

Please note that we are in the process of moving away from hand-written ffi code and instead favouring the use of the uniffi library.

List of components

  • autofill - for storage and syncing of credit card and address information
  • crashtest - testing-purposes (crashing the Rust code)
  • fxa-client - for applications that need to sign in with FxA, access encryption keys for sync, and more.
  • logins - for storage and syncing of a user's saved login credentials
  • nimbus - for integrating with Mozilla's experimentation platform for Firefox
  • places - for storage and syncing of a user's saved browsing history
  • push - for applications to receive real-time updates via WebPush
  • rc_log - for connecting component log output to the application's log stream
  • support - low-level utility libraries
  • sync15 - shared library for accessing data in Firefox Sync
  • sync_manager - integrates multiple sync engines/ stores into a single framework
  • tabs - an in-memory syncing engine for remote browser tabs
  • viaduct - an HTTP request library
  • webext-storage - powers an implementation of the WebExtension API