A. PXID stands for “Permutive Cross-Domain ID”. It is a third-party cookie, set by Permutive, which is used to identify users across multiple domains owned by a given Publisher.
Typically, it is enabled when a Publisher owned multiple domains and has an interest in identifying their users consistently across their domains. The URL of the referrer header has to match a pre-configured list of domains (configured in the Permutive dashboard). We refer to this service as the “Secure Permutive 3P cookie”, and will not be shared between Publishers. This PXID 3P cookie varies Publisher by Publisher.