Some online advertising has been based on showing an ad to a potentially-interested person who has previously interacted with the advertiser or ad network. Historically this has worked by the advertiser recognizing a specific person as they browse across web sites, a core privacy concern with today's web.

The TURTLEDOVE effort is about offering a new API to address this use case while offering some key privacy advances:

• The browser, not the advertiser, holds the information about what the advertiser thinks a person is interested in.
• Advertisers can serve ads based on an interest, but cannot combine that interest with other information about the person — in particular, with who they are or what page they are visiting.
• Web sites the person visits, and the ad networks those sites use, cannot learn about their visitors' ad interests.

Chrome expects to build and ship a first experiment in this direction during 2021. For details of the current design, see FLEDGE.

The FLEDGE design draws on many discussions and proposals published during 2020, most notably:

• The original TURTLEDOVE from Chrome.
• SPARROW from Criteo, which entered WICG incubation jointly with TURTLEDOVE.
• Outcome-based TURTLEDOVE and Product-level TURTLEDOVE from RTB House.
• Dovekey from Google Ads.
• PARRROT from Magnite.
• TERN from NextRoll.

Many additional contributions came from Issues opened in this repo, and from discussion in the W3C Web Advertising Business Group.