Chrome plans to obsolete third-party cookies, therefore developers need the ability to use cookies in third-party contexts that are partitioned by top-level site. This is necessary for use cases that are not cross-site tracking related. For example, SaaS embeds, headless CMS, and sandbox domains). The CHIPS cookie attribute of `Partitioned` enables developers to opt into having their third-party cookies partitioned by top-level site.
New browser privacy models restrict sites' ability to track user activity across top-level contexts, and Chrome plans on blocking cross-site cookies available to third-parties in multiple top-level contexts. Although these cross-site cookies are now widely recognized as being a cross-site tracking mechanism, there are several other use cases for cross-party cookies on the web today, e.g. SaaS embeds, headless CMS, sandbox domains, etc. In order to support the non-tracking-related use cases for third-party cookies above, we plan to introduce a new cookie attribute, Partitioned, to support cross-site cookies that are partitioned by top-level context, i.e. partitioned by top-level site (or that site's First-Party Set if it has one). These cookies will not be restricted by cross-site cookie blocking since they cannot be used to track users' activity across different sites.
Docs: https://docs.google.com/document/d/1wL2lCXpaVOi0cWOn_ehfLFIZQxT3t0SH-ANnZYPEB0I/edit
Explainers: https://github.com/privacycg/CHIPS