The Protected Audience API provides 2 mechanisms that allow signals to be passed into auctions in such a way that ensures the authenticity and integrity of the signals: the original version [0], which used subresource web bundles [1] to contain the signals, and the subsequent version [2], which used special HTTP response headers on page-initiated fetch() requests. This deprecation and removal is only for the original, subresource web bundle version, and does not affect the response header version. Use counter metrics [3] show the feature is used on less than 1 in 500 million page loads. Deprecating and removing the original subresource web bundle version of directFromSellerSignals will improve code health and remove potential attack surfaces. [0] https://github.com/WICG/turtledove/blob/main/FLEDGE.md#251-using-subresource-bundles [1] https://github.com/WICG/webpackage/blob/main/explainers/subresource-loading.md [2] https://github.com/WICG/turtledove/blob/main/FLEDGE.md#252-using-response-headers [3] https://chromestatus.com/metrics/feature/timeline/popularity/5034