Why Does My Public IP Address Change?

• Dynamic ISP assignment: the provider can allocate a different address when a connection or lease changes. Renewing a lease can also keep the same address; there is no universal rotation schedule.
• Switching Wi-Fi, mobile data or hotspots changes the network used for the request.
• A VPN, proxy or privacy relay can select a different public exit address.
• IPv6 temporary addresses can change even when the network prefix stays the same. The ISP may separately change the prefix assigned to your router.

1. Compare the address family first. An IPv4 result and an IPv6 result can both belong to the same connection at the same time.
2. Record the time, network and VPN/relay state with each result. Avoid comparing a browser using a relay with a command-line client using a direct connection.
3. Distinguish your device's local address from the public address. Renewing the laptop's local DHCP lease does not necessarily change the router's public address.

Ask your ISP whether a static public address is available if a third party needs a fixed address for an allowlist. A DHCP reservation in your home router stabilizes a local address, not the ISP-facing public address.

Dynamic DNS can keep a hostname pointed at a changing address, but it does not open firewall rules or remove carrier-grade NAT. For remote access, use an authenticated access method and check whether the connection is reachable first.

Several people can share a public address and one person can use many addresses. Use accounts or appropriate authentication for identity, rather than treating an unchanged IP as proof that a user is the same person.

• RFC 2131: DHCP address allocation and leases
• RFC 8981: Temporary IPv6 addresses
• RFC 6598: Shared Address Space
• Apple: Private Relay