Messaging System


Firefox must be an opinionated user agent that keeps folks safe, informed and effective while browsing the Web. In order to have an opinion, Firefox must have a voice.

That voice will respect the user’s attention while surfacing contextually relevant and timely information tailored to their individual needs and choices.

What does Messaging System support?

There are several key windows of opportunity, such as the first-run activation phase or coordinated feature releases, where Firefox engages with users.

The Firefox Messaging System supports this engagement by targeting messages exactly to the users who need to see them and enables the development of new user messages that can be easily tested and deployed. It offers standard mechanisms to measure user engagement and to perform user messaging experiments with reduced effort across engineering teams and a faster delivery cycle from ideation to analysis of results.

This translates to users seeing fewer and more relevant in-product messages, while supporting fast delivery, experimentation, and protection of our users time and attention.

Messaging System Overview

At the core of the Firefox Messaging System is the Messaging System Router (called ASRouter for historical reasons). The router is a generalized Firefox component and set of conventions that provides:

  • Flexible and configurable routing of local or remote Messages to UI Templates. This allows new message campaigns to be started and controlled on or off-trains

  • Traffic Cop message sequencing and intermediation to prevent multiple messages being concurrently shown

  • Programmable message targeting language to show the right message to the right user at the right time

  • A template library of reusable Message and Notification UIs

  • Full compatibility with Normandy pref-flip experiments

  • Generalized and privacy conscious event telemetry

  • Flexible Frequency Capping to mitigate user message fatigue

  • Localized off train Messages

  • Powerful development/debugging/QA tools on about:asrouter

Message Routing

Message Routing Overview

The Firefox Messaging System implements a separation-of-concerns pattern for Messages, UI Templates, and Timing/Targeting mechanisms. This allows us to maintain a high standard of security and quality while still allowing for maximum flexibility around content creation.

UI Templates

We have built a library of reusable Notification and Message interfaces which land in the Firefox codebase and ride the trains. These templates have a defined schema according to the available design components (e.g. titles, text, icons) and access to a set of enhanced user actions such as triggering URLs, launching menus, or installing addons, which can be attached to interactive elements (such as buttons).

Current templates include:

Detailed Docs