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Addons-frontend 🔥

Code of Conduct CircleCI codecov Documentation

Front-end infrastructure and code to complement mozilla/addons-server.

Security Bug Reports

This code and its associated production website are included in Mozilla’s web and services bug bounty program. If you find a security vulnerability, please submit it via the process outlined in the program and FAQ pages. Further technical details about this application are available from the Bug Bounty Onramp page.

Please submit all security-related bugs through Bugzilla using the web security bug form.

Never submit security-related bugs through a Github Issue or by email.


  • You need Node 16.x which is the current LTS (long term support) release.
  • Install yarn to manage dependencies and run scripts.

The easiest way to manage multiple node versions in development is to use nvm.

Get started

If you are on Windows, please make sure to follow windows guidelines too.

  • type yarn to install all dependencies
  • type yarn amo:stage to start a local server that connects to a hosted staging server

Development commands

Here are some commands you can run:

Command Description
yarn amo:olympia Start the dev server/proxy (for amo) using data from a local addons-server environment.
yarn amo:dev Start the dev server/proxy (for amo) using data from the dev server (
yarn amo:dev-https Same as amo:dev but with HTTPS, available at: Read about setting up this environment
yarn amo:stage Start the dev server/proxy (for amo) using data from the staging server (
yarn build Build the app.
yarn build-ci Run the build and bundlewatch npm scripts.
yarn bundlewatch Run bundlewatch to check the generated AMO bundle sizes. Building AMO is required first.
yarn flow Run Flow. By default this checks for errors and exits
yarn flow:check Explicitly check for Flow errors and exit
yarn flow:dev Continuously check for Flow errors
yarn eslint Lint the JS
yarn start-func-test-server Start a Docker container for functional tests
yarn stylelint Lint the SCSS
yarn lint Run all the JS + SCSS linters
yarn prettier Run Prettier to automatically format the entire codebase
yarn prettier-dev Run [Pretty-Quick][] to automatically compare and format modified source files against the master branch
yarn prettier-ci Run Prettier and fail if some code has been changed without being formatted
yarn version-check Check you have the required dependencies
yarn test Run all tests (Enters jest in --watch mode)
yarn test-debug Run all tests with full console output and full error messages (Enters jest in --watch mode)
yarn test-coverage Run all tests and generate code coverage report (Enters jest in --watch mode)
yarn test-coverage-once Run all tests, generate code coverage report, then exit
yarn test-once Run all tests, run all JS + SCSS linters, then exit
yarn test-ci Run all continuous integration checks. This is only meant to run on CI.

Running tests

You can enter the interactive jest mode by typing yarn test or yarn test-debug. This is the easiest way to develop new features.

Here are a few tips:

  • yarn test will hide most console output and detailed test failure messages, so it is best when you are running a full suite of tests. When working on an individual test, you likely want to run yarn test-debug.
  • When you start yarn test, you can switch to your code editor and begin adding test files or changing existing code. As you save each file, jest will only run tests related to the code you change.
  • If you had typed a when you first started then jest will continue to run the full suite even when you change specific files. Type o to switch back to the mode of only running tests related to the files you are changing.
  • Sometimes running tests related to your file changes is slow. In these cases, you can type p or t to filter tests by name while you working fixing a specific test suite. More info.
  • If you see something like Error watching file for changes: EMFILE on Mac OS then brew install watchman might fix it. See jestjs/jest#1767

Run a subset of the tests

By default, yarn test will only run a subset of tests that relate to the code you are working on.

To explicitly run a subset of tests, you can type t or p which are explained in the jest watch usage.

Alternatively, you can start the test runner with a specific file or regular expression, like:

yarn test tests/unit/amo/components/TestAddon.js

Run all tests

If you want to run all tests and exit, type:

yarn test-once


As you run tests you will see a report of Eslint errors at the end of the test output:

yarn test

If you would like to run tests without Eslint checks, set an environment variable:

NO_ESLINT=1 yarn test


There is limited support for using Flow to validate the intention of our program.

As you run tests you will see a report of Flow errors at the end of the test output:

yarn test

If you would like to run tests without Flow checks, set an environment variable:

NO_FLOW=1 yarn test

To only check for Flow issues during development while you edit files, run:

yarn flow:dev

If you are new to working with Flow, here are some tips:

To add flow coverage to a source file, put a /* @flow */ comment at the top. The more source files you can opt into Flow, the better.

Here is our Flow manifesto:

  • We use Flow to declare the intention of our code and help others refactor it with confidence. Flow also makes it easier to catch mistakes before spending hours in a debugger trying to find out what happened.
  • Avoid magic Flow declarations for any internal code. Just declare a type alias next to the code where it's used and export/import it like any other object.
  • Never import a real JS object just to reference its type. Make a type alias and import that instead.
  • Never add more type annotations than you need. Flow is really good at inferring types from standard JS code; it will tell you when you need to add explicit annotations.
  • When a function like getAllAddons takes object arguments, call its type object GetAllAddonsParams. Example:
type GetAllAddonsParams = {|
  categoryId: number,

function getAllAddons({ categoryId }: GetAllAddonsParams = {}) {
  • Use Exact object types via the pipe syntax ({| key: ... |}) when possible. Sometimes the spread operator triggers an error like 'Inexact type is incompatible with exact type' but that's a bug. You can use the Exact<T> workaround from src/amo/types/util if you have to. This is meant as a working replacement for $Exact.
  • Add a type hint for components wrapped in HOCs (higher order components) so that Flow can validate calls to the component. We need to add a hint because we don't yet have decent type coverage for all the HOCs we rely on. Here is an example:
// Imagine this is something like components/ConfirmButton/index.js
import { compose } from 'redux';
import * as React from 'react';

// This expresses externally used props, i.e. to validate how the app would use <ConfirmButton />
type Props = {|
  prompt?: string | null,

// This expresses internally used props, such as i18n which is injected by translate()
type InternalProps = {|
  i18n: I18nType,

export class ConfirmButtonBase extends React.Component<InternalProps> {
  render() {
    const prompt = this.props.prompt || this.props.i18n.gettext('Confirm');
    return <button>{prompt}</button>;

// This provides a type hint for the final component with its external props.
// The i18n prop is not in external props because it is injected by translate() for internal use only.
const ConfirmButton: React.ComponentType<Props> = compose(translate())(

export default ConfirmButton;
  • Try to avoid loose types like Object or any but feel free to use them if you are spending too much time declaring types that depend on other types that depend on other types, and so on.
  • You can add a $FlowFixMe comment to skip a Flow check if you run into a bug or if you hit something that's making you bang your head on the keyboard. If it's something you think is unfixable then use $FlowIgnore instead. Please explain your rationale in the comment and link to a GitHub issue if possible.
  • If you're stumped on why some Flow annotations aren't working, try using the yarn flow type-at-pos ... command to trace which types are being applied to the code. See yarn flow -- --help type-at-pos for details.


We use Prettier to automatically format our JavaScript code and stop all the on-going debates over styles.

Code coverage

To see a report of code coverage, type:

yarn test-coverage-once

This will print a table of files showing the percentage of code coverage. The uncovered lines will be shown in the right column but you can open the full report in a browser:

open coverage/lcov-report/index.html

Running AMO for local development

A proxy server is provided for running the AMO app with the API on the same host as the frontend. This mimics our production setup.

Start developing against a hosted API like this:

yarn amo:dev

This configures the proxy to use for API data. This command is the most common way to develop new frontend features. See the table of commands up above for similar ways to run the server.

To use a local API server running in Docker, you can use the yarn amo command. However, this is currently not working. See issue-7196.

Authentication will work when initiated from addons-frontend and will persist to addons-server but it will not work when logging in from an addons-server page. See mozilla/addons-server#4684 for more information on fixing this.

Local configuration

If you need to override any settings while running yarn amo, yarn amo:dev, or yarn amo:stage, first create a local config file named exactly like this:

touch config/local-development.js

Make any config changes. For example:

module.exports = {
  trackingEnabled: true,

Restart the server to see it take affect.

Consult the config file loading order docs to learn more about how configuration is applied.

Configuring an Android device for local development

If you want to access your local server on an Android device you will need to change a few settings. Let's say your local machine is accessible on your network at the IP address You could start your server like this:

    yarn amo:dev

On your Android device, you could then access the development site at

NOTE: At this time, it is not possible to sign in with this configuration because the Firefox Accounts client redirects to localhost:3000. You may be able to try a different approach by editing /etc/hosts on your device so that localhost points to your development machine but this has not been fully tested.

Disabling CSP for local development

When developing locally with a webpack server, the randomly generated asset URL will fail our Content Security Policy (CSP) and clutter your console with errors. You can turn off all CSP errors by settings CSP to false in any local config file, such as local-development-amo.js. Example:

module.exports = {
  CSP: false,

Working on the documentation

The documentation you are reading right now lives inside the source repository as Github flavored Markdown. When you make changes to these files you can create a pull request to preview them or, better yet, you can use grip to preview the changes locally. After installing grip, run it from the source directory like this:

grip .

Open its localhost URL and you will see the rendered file. As you make edits, it will update automatically.

Building and running services

The following are scripts that are used in deployment - you generally won't need unless you're testing something related to deployment or builds.

The env vars are:

  • NODE_ENV: the node environment, e.g. production or development
  • NODE_CONFIG_ENV: the name of the configuration to load, e.g., dev, stage, prod
Script Description
yarn start Starts the express server (requires env vars)
yarn build Builds the libs (all apps) (requires env vars)

Example: Building and running a production instance of the app:

NODE_ENV=production NODE_CONFIG_ENV=prod yarn build
NODE_ENV=production NODE_CONFIG_ENV=prod yarn start

Running builds locally

To run the app locally in production mode you'll need to create a config file for local production builds. Production builds can be built for different environments: dev, stage and prod (controlled by the NODE_CONFIG_ENV env var), but only one extra config file is needed for these environments to run locally.

Rename the file named config/local.js.dist to config/local.js. After this, re-build and restart using yarn build and yarn start as documented above. If you have used before with a different configuration, be sure to clear your cookies. The application should be available at:

NOTE: At this time, it's not possible to sign in using this approach.

What version is deployed?

You can check to see what commit of addons-frontend is deployed, which A/B experiments are running, or which feature flags are enabled by making a request like this:

    "build": "",
    "commit": "47edfa6f24e333897b25516c587f504e294e8fa9",
    "experiments": {
        "homeHero": true
    "feature_flags": {
        "enableFeatureAMInstallButton": true,
        "enableFeatureStaticThemes": true
    "source": "",
    "version": ""

This will return a 415 response if a version.json file doesn't exist in the root directory. This file is typically generated by the deploy process.

For consistency with monitoring scripts, the same data can be retrieved at this URL:


💡 You can install the amo-info extension to easily view this information.

Addons Frontend Blog Utils

This project also contains code to build a library named addons-frontend-blog-utils and offers the following commands:

  • yarn build:blog-utils-dev: build the library, start a watcher to rebuild the library on change and serve a development page at
  • yarn build:blog-utils-prod: build the library in production mode

This library is exclusively designed to work with addons-blog.

Release process

In order to publish a new version of addons-frontend-blog-utils, a special tag has to be pushed to the main repository. The tag name must start with blog-utils- and usually contains the version number. This can be automated using the following command:

npm version [major|minor|patch]

Issuing this command from the master branch will update the version in the package.json, create a commit and create a tag. Push both this commit and the tag to the main repository.

Note: When a new addons-frontend-blog-utils release is merged in addons-blog, you should publish a new version of the WordPress theme. Please follow these instructions in the addons-blog repository.

Core technologies

  • Based on Redux + React
  • Code written in ES2015+
  • Universal rendering via node
  • Unit tests with high coverage (aiming for 100%)