Abstract: Embodiments disclosed herein relate to systems, devices, and methods for determining the Internet Protocol Version 4 (IPv4) address and the Internet Protocol Version 6 (IPv6) address of a purported end user device to use for detection and filtering of invalid traffic (IVT). In an exemplary embodiment, a method comprises receiving, at a domain only supporting IPv4, a request from the purported end user device over a network, wherein the purported end user device comprises an IPv6 address and an IPv4 address. The method further comprises redirecting, by the domain only supporting IPv4, the request to a domain supporting IPv6. The method further comprises measuring ad traffic and/or performing user tracking using the IPv4 and IPv6 addresses and fulfilling the request from the purported end user device.