[shostack]

Cookie onboarding services are nothing new. To start, look at a company like LiveRamp. They ask sites that get users to authenticate to login, then you provide them with an anonymous hashed email address of the user which they match with they then use to match against a larger cookie pool. If there's a match, they set another cookie.

This helps solve the issue for advertisers using retargeting where cookies don't have a long shelf life. So they leverage 2nd party data sources to basically set those cookies again for them so they can continue retargeting.

They can also work with vendors to upload their hashed email lists from their CRMs and gain access to the relevant cookies in the pool to market to them.

Onboarding vendors like this tend to pay a CPM rate based on the number of matches they can make with their cookie pool, so really all that matters is that you have a massive number of people authenticating with email addresses.