Retargeting, an online advertising tactic, is based on showing ads to users who have previously interacted with an advertiser website or have left the website without taking a specified action. The advertiser can then serve ads to a specific user based on their prior behavior, which is one of the primary privacy concerns among users today.

To address this specific use case, Google has announced a new Privacy Sandbox initiative called Turtledove. Turtledove works similar to Google’s other Privacy Sandbox initiative, FLoC, in that the browser, not the advertiser, holds information about the user. The Turtledove API uses information about brands a user has previously expressed interest in and information about the current page to send two ad requests – one request for ads based on interests as defined by the advertiser and another request for ads based on contextual data from the current page.

After the API requests are made, the browser runs an auction to determine the most relevant ad by using JavaScript code provided by the advertiser. The ad deemed as most relevant is then served to the user. Like FLoC, Turtledove appears to strike the balance of appeasing both user privacy concerns as well as the needs of advertisers. Only time will tell if this type of replacement technology will allow advertisers to continue to deliver meaningful results to clients in a cookieless world.