Masked Domain List Overview

The Masked Domain List (MDL) is a publicly available list of domains that is hosted on GitHub. MDL domains are identified by Disconnect.me based on criteria provided by Google. It is used by Chrome's IP Protection feature to mask a user's IP address when a listed domain is accessed in a third-party context within Incognito mode.

MDL inclusion criteria

The MDL consists of domains that fulfill the following criteria:

The domain is embedded as a third-party domain and therefore in a position to collect information about a user or their device across multiple sites that aren't owned by the data collector (in the detailed explainer you can read about how we plan to identify ownership).

In addition, the domain also meets at least one of the following criteria:

  • The domain serves one of the following business purposes:
    • Serving of ads
    • Targeting of ads
    • Measuring ad effectiveness
    • Collection of user data for ads, commerce or marketing related activities

OR

  • The domain collects user or device information in a way that appears likely to support re-identification of users or devices across contexts.

Additionally Chrome has developed a methodology to identify widely used JavaScript functions that can provide sufficiently unique and stable information from web APIs to be used to identify users. JavaScript functions like this can be detected when they are loaded in a third-party context. The origin of the JavaScript can then be added to the MDL and proxied in subsequent requests.

When the Script Blocking feature is enabled, Chrome will check network requests against the blocklist. When there is a match, active content from those domains will be blocked (for example, scripts, iframes), but not static resources (for example, images or stylesheets). This feature will affect entries marked "Impacted by script blocking".

The detection pipeline operated by Google that looks for these patterns of API misuse considers all domains, including Google's own domains.

Periodically, domains may be added or removed based on the detection pipeline and updates to Disconnect.me's published list. Domains that have successfully obtained an appeal will be removed from MDL. The most-recently published MDL is the version used by Chrome.

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