For the past few years, Firefox has been working on privacy tech with their Enhanced Tracking Protection technology, and as part of that work, they undertook development to strip query string parameters from the URL in much the same way we’ve seen from Brave. The feature was first seen in Firefox 90, entered testing in Firefox 96, and received general release on June 28th, 2022 as part of the deployment of Firefox 102.
What’s the Impact?
The feature is presently part of the ‘Strict’ setting, which must be manually activated by the user.
Once enabled, any top level navigation event (opening a new tab or window, clicking on links, or redirects between URLs) will remove a list of query parameters from the destination URL, preventing the parameters from being present and thus campaign / tracking measurement will attribute such traffic to a Direct marketing channel. If specific functionality is dependent on such parameters, it may not function as expected if they are missing.
Prior to the shift to a remote service list managed by Firefox, the initial list contained the following parameters:
pref("privacy.query_stripping.strip_list", "mc_eid oly_anon_id oly_enc_id __s vero_id _hsenc mkt_tok fbclid");This means that at minimum, attribution to Facebook, Marketo, HubSpot, Vero, Drip and Olytics would be adversely impacted for Firefox traffic with the feature enabled. Further, this will contribute to a larger delta when comparing advertiser clicks (for example) with analytics systems as the Advertiser will count a click which won’t be properly attributed / seen by the analytics platform. Lastly, since the list is now managed remotely, the Firefox team can adjust it at any time to add support for additional tracking vendors.
Adding Parameters
Firefox also allowed users to add to that list on their local machines, by adding support for the privacy.query_stripping.strip_list preference, which can be accessed from the URL by typing in about:config. This means that users who leverage this feature may suppress more tracking information than just the base list on offer from Firefox.
Conclusion
Analysts and Marketers should be aware that going forward users of Firefox 102 or higher may not accurately reflect marketing channel attribution for at least the above channels. Further, it should be considered that this may be an initial first step for Mozilla, and that the ultimate intent is to shift the feature to a default setting down the road, as they did with Total Cookie Protection.