Stub Attribution is a process that enables the construction and transmission of marketing attribution code on www.mozilla.org. When a user visits a mozilla.org download page, the website constructs an attribution code, which is then passed to download.mozilla.org via a URL parameter. This attribution code is then passed to the Windows stub installer, where it finally gets passed to Firefox for use in Telemetry. This attribution funnel enables Mozilla to better understand how different marketing campaigns effect overall retention in Firefox.
How does it work in bedrock?¶
The base template in bedrock contains a stub attribution script that runs on every page of the website. The script only runs on Windows (since the stub installer is a Windows feature) and if cookies are enabled. The script also respects Do Not Track, so it will not run if the user agent has this flag set.
The stub attribution script looks for utm_* params on the page URL as well as the referrer, and then creates a hash of that data by passing it to an authentication service in bedrock. This hash is then accompanied by a signed, encrypted signature to prove that the data came from a trusted source. Both pieces of authenticated data are then stored in a cookie.
Once the user reaches the download page, bedrock then checks if the cookie exists, and if so appends the authenticated data to the download URL. The rest of the process is handled by the download service and stub installer.
For stub attribution to work locally or on a demo instance, a value for the HMAC key that is used to sign the attribution code must be set via an environment variable e.g.
This value can be anything if all you need to do is test the bedrock functionality. It only needs to match the value used to verify data passed to the stub installer for full end-to-end testing via Telemetry.
Measuring campaigns and experiments¶
Stub Attribution was originally designed for measuring the effectiveness of marketing campaigns where the top of the funnel was outside the remit of www.mozilla.org. For these types of campaigns, stub attribution requires zero configuration. It just works (as configured in /media/js/base/stub-attribution.js) in the background and passes along any attribution data that exists.
More recently, the ability to measure the effectiveness of experiments was also added
as a feature. This is achieved by adding optional
Mozilla.StubAttribution.experimentName = 'experiment-name'; Mozilla.StubAttribution.experimentVariation = 'v1';
it must be done prior to calling