Google Federated Learning of Cohorts (FLoC) – optout

Google Chrome 89 and other browsers based upon it such as Chromium Edge have introduced a new capability known as FLoC. This approach removes the need for third-party cookies by passing a group identifier in the HTTP Headers in a manner similar to how Cookies are exchanged. While FLoC should allow for users to remain more anonymous as advertisers only receive a group identifier for the user, it would not be difficult to use their IP address or other features available via device fingerprinting to track the individual.

As a web user, you would need to use several approaches to avoid this:
1. Use a browser without FLoC support. Hopefully, this will be added to the configuration menus to allow users to prevent it, similar to DNT.
2. Use a browser plugin (or other software/proxy) to remove the FLoC headers.

As a web-developer, you can add configuration to opt-out of all FLoC cohort calculation by sending the following HTTP response header:

Permissions-Policy: interest-cohort=()

If you really want to see the data, the following javascript will expose it:

const { id, version } = await document.interestCohort();
console.log('FLoC ID:', id);
console.log('FLoC version:', version);


Mozilla Firefox Tracking Protection

While “Do Not Track” (DNT) was an HTTP Header used to “request” that the browser sent to a server, it was not guaranteed to be honored. New versions of Firefox support “Tracking Protection” that automatically block many common tracking mechanisms.

  • Type “about:config” in the URL line.
  • Toggle “privacy.trackingprotection.enabled” from false to true.
  • Done!


Do Not Track (DNT) HTTP Header

Over the past year there have been many capabilities added to web browsers to allow users to indicate their willingness to be tracked across various sites for web advertisements. While the implementation by individual hosts is optional, the user can sent the request to identify their personal preference. Tracking can be relevant to allow for more “targeted” ads tailored to each user.

Firefox 4.0 betas added an "X-Do-Not-Track:1" HTTP Header. Later implemented Firefox 5.0 betas as "DNT:1". Safari and MSIE9 have also added support. Recently Firefox 9.0 exposed this attribute to JavaScript as navigator.doNotTrack, with a value of “yes” when set.