IPv6 privacy addresses (sometimes called temporary addresses) were specifically designed to address a real tracking concern unique to IPv6's larger address space — worth understanding both what they fix and what they don't.
The concern they were designed to fix
Early IPv6 implementations often derived a device's interface identifier from its hardware MAC address, meaning a device could carry a stable, identifiable portion of its address across different networks over time — a genuine, meaningful tracking signal that doesn't have a real equivalent in typical IPv4 usage.
How the rotation actually works
Privacy addresses generate a randomized interface identifier instead, and rotate it periodically (commonly daily, though the interval is configurable) — meaning the device-specific portion of your IPv6 address changes over time rather than remaining a stable, trackable identifier.
What rotation does not change
The network prefix — the portion of the address identifying your ISP and general network — stays the same regardless of interface-identifier rotation. This means privacy addresses limit device-level tracking across sessions, but don't hide your general network or approximate location, since the prefix alone still carries that information. See IPv6 Geolocation and Prefix Assignment.
Why this is a genuine but partial privacy improvement
Privacy addresses solve a specific problem (device-level identifier stability) without solving a different one (network-level location and ownership visibility) — worth understanding as a meaningful but incomplete measure, not a comprehensive anonymity feature.
FAQ
Are privacy addresses enabled by default?
On most current major operating systems, yes — though the specific rotation interval and default behavior can vary by platform and version.