Google Consent with ATP (Ad Tech Providers)
Google’s Additional Consent Mode technical specification, or Additional Consent Mode (AC String), is a temporary technical specification that alongside IAB TCF v2.0. is used to serve as a bridge for vendors who are not yet registered on the IAB Europe Global Vendor List (GVL).
It enables publishers, Consent Management Providers (CMPs), and partners to gather and propagate additional consent—alongside their TCF v2.0 implementation—for companies that are on Google's Ad Tech Providers (ATP) list however not yet registered with the IAB Europe Global Vendor List (GVL).
The AC String may only be created by an IAB Europe TCF-registered CMP using its assigned CMP ID number in accordance with the IAB Policies. The AC string cannot be created by Vendors or any other third-party service providers themselves.
An AC string may only be created where the publisher is in compliance with Google’s EU User Consent Policy. Most importantly, an AC string should not be created before the user has given legally valid consent to:
The use of cookies or other local storage where legally required
The collection, sharing, and use of personal data for personalization of ads by an ATP in accordance with Google’s EU User Consent Policy
Check out the full technical specification here.
An AC string cannot replace a TC string, it is only a supplemental string to the TC string. This means that Google will discard the AC string on a request received if a TC string is not available for the same request.