Price Wise is a Firefox extension that spots price drops on things you’re interested in.
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Latest commit 1c5ab79 Dec 5, 2018

Price Wise

Price Wise is a Firefox extension that tracks price changes to help you find the best time to buy.

Data Collection


Developer Setup


  • A recent version of Node.js and NPM
  1. Clone the repository:

    git clone
    cd price-wise
  2. Install dependencies:

    npm install
  3. Build the extension:

    npm run build
  4. Run the built extension in a test browser:

    npm start

Note: This will install the extension as an unsigned WebExtension Experiment.

  • Unsigned WebExtension Experiments can only be run in Nightly and DevEdition with boolean about:config preferences xpinstall.signatures.required set to false and extensions.legacy.enabled set to true.
  • To test an unsigned WebExtension Experiment in Firefox Beta or Release, an unbranded build must be used.


Command Description
npm start Launch Firefox with the extension temporarily installed
npm run lint Run linting checks
npm run build Compile source files with Webpack using a development configuration
npm run build:prod Compile source files with Webpack using a production configuration
npm run watch Watch for changes and rebuild with Webpack using a development configuration
npm run watch:prod Watch for changes and rebuild with Webpack using a production configuration
npm run package Package the extension into an XPI file
pipenv run test Run test suite (See "Running Tests" for setup)

Data Storage

Global state for the add-on is managed via Redux. Any time the data is changed, it is persisted to the add-on local storage.

Reducers, action creators, etc. are organized into ducks inside the src/state directory.


Running Tests

Automated tests are run in a Firefox browser instance using Marionette. We use the Python client for Marionette since there is no up-to-date JavaScript client.

To set up your environment for running the tests, you must have:

  • A Firefox binary. On MacOS, this can be found within the .app folder at
  • Python 2.7
  • Pipenv

With these installed, you can set up the test suite:

  1. Install Python dependencies:

    pipenv install
  2. Save the path to your Firefox binary with npm:

    npm config set price-wise:firefox_bin <PATH_TO_FIREFOX_BINARY>

After this, you can run pipenv run test to run the automated test suite.


The following preferences can be set to customize the extension's behavior for testing purposes. Some convenient testing values can be found in web-ext-config.js, and will be used by default with npm start.
(string) List of domains ({Array.string} or *) that extraction is performed on. Can be set to * to enable extraction on all sites.
(integer) Time to wait between price checks for a product in milliseconds.
(integer) Time to wait between checking if we should fetch new prices in milliseconds.
(integer) Delay before removing iframes created during price checks in milliseconds.
(integer) The percentage drop in price on which to trigger a price alert compared to the last high price (See price_last_high in [](./docs/
(integer) The absolute drop in price on which to trigger a price alert compared to the last high price (see `price_last_high` in [](./docs/ in currency subunits (e.g. cents for USD).

Releasing a New Version

Price Wise bumps the major version number for every release, similar to Firefox. Releases are created by tagging a commit that bumps the version number and pushing that tag to the repo. This triggers CircleCI automation that packages, tests, signs and uploads the new version to the Test Pilot S3 bucket.

It is strongly recommended that developers creating releases configure Git to sign their commits and tags.

To create a new release of Price Wise:

  1. Increment the version number in package.json, create a new commit on the master branch with this change, and create a new git tag pointing to the commit with a name of the form v1.0.0, where 1.0.0 is the new version number.

    npm ships with a command that can perform these steps for you automatically:

    npm version major
  2. Push the updated master branch and the new tag to the remote for the Mozilla Price Wise repository (named origin in the example below):

    git push origin master
    git push origin v1.0.0

You can follow along with the build and upload progress for the new release on the CircleCI dashboard. Once the build finishes, a signed copy of the new version will be available in the dashboard under Artifacts. The following upload job, however, is gated on a hold job.

This hold job is intended to provide developers and QA an opportunity for final testing and review of the extension in release channels before uploading. When QA is satisfied, a developer with push access must manually trigger the upload to Test Pilot via the CircleCI dashboard by clicking the hold job and approving the build.

Once the upload is complete, the new version should be available immediately at


The Commerce WebExtension is licensed under the MPL v2.0. See LICENSE for details.