https://groups.google.com/a/chromium.org/g/blink-dev/c/9s8ojrooa_Q posted:

IP Protection is a feature that sends third-party traffic for a set of domains through proxies for the purpose of protecting the user by masking their IP address from those domains.

After receiving much feedback from the ecosystem, the design of the broader proposal is as follows:

* IP Protection will be opt-in initially. This will help ensure that there is user control over privacy decisions and that Google can monitor behaviors at lower volumes.

* It will roll out in a phased manner. Like all of our privacy proposals, we want to ensure that we learn as we go and we recognize that there may also be regional considerations to evaluate.

* We are using a list based approach and only domains on the list in a third-party context will be impacted. We are conscious that these proposals may cause undesired disruptions for legitimate use cases and so we are just focused on the scripts and domains that are considered to be tracking users.

We plan to test and roll out the feature in multiple phases. To start, Phase 0 will use a single Google-owned proxy and will only proxy requests to domains owned by Google. This first phase will allow us to test our infrastructure while preventing impact to other companies and gives us more time to refine the list of domains that will be proxied. For simplicity, only clients with US-based IP addresses will be granted access to the proxies for phase 0.

A small percentage of clients will be automatically enrolled in this initial test, though the architecture and design will evolve between this test and future launches. To access the proxy, a user must be logged in to Chrome. To prevent abuse, a Google-run authentication server will grant access tokens to the Google run proxy based on a per-user quota.

In future phases we plan to use a 2-hop proxy, as had previously been indicated in the IP Protection explainer.