Ad slot size in real-time bidding signals fetch: Protected Audience ad selection auctions allow buyers to fetch real-time signals from their key-value server. Besides being used for calculating bid prices, these signals can also be used for prioritizing and filtering potential ad candidates. The more ad candidate filtration and prioritization that we can enable, the more performant the auction is (e.g. less browser resource utilization) and the higher the quality of the chosen ad candidates is. This feature extends the signals about the page where the ad will be displayed from just its domain name, to also include the size of the ad slots on the page, which is a very useful signal for filtering out ads that cannot be rendered in that slot size. Allow updating interest group’s userBiddingSignals and executionMode: Protected Audience has always supported updating interest group fields, but for historical reasons did not support updating the interest group field named userBiddingSignals, and for no obvious reason did not support updating executionMode. This change is a small extension to Protected Audience interest group updating to support updating these fields, making the API more useful by being able to update/refresh the fields with more up to date information.
Explainers: https://github.com/WICG/turtledove/pull/928