Quote:In the latest move to improve the privacy of the Chrome browser, Google is adding support for a new HTML tag that prevents user tracking by isolating embedded content from the page embedding it.
 
Currently, web browsers allow third-party iframes to communicate with their embedding page. This can be done using postMessage, attributes (e.g., size and name), and permissions.
 
With browser developers restricting third-party cookies to prevent user tracking, advertising companies have proposed different programming APIs that advertisers can use for interest-based advertising.
 
These new interest-based advertising technologies include Google's FLoC, Microsoft's PARAKEET, and Facebook's Conversion Lift.
 
However, when third-party cookies have been removed, these technologies should not be possible to track users by the cross-joining of data between an iframe and its embedder.
 
To prevent this, Google is adding a new form of embedded iframe called a "fenced frame" to isolate the embedded content and not allow it to see the user data of the embedding page.
 

Adding Fenced Frames to Google Chrome