Your IP address changes because most internet providers and home routers hand out addresses dynamically: each address is leased for a limited time, and a new one can be assigned when the lease expires, your router reconnects, you move between networks or you turn on a VPN. If you need an address that never changes, you have to ask for a static IP or use a service that does not depend on your IP at all.
There are really two different addresses that can change, and they change for different reasons. Your public IP address is the one websites see, and it is assigned by your internet service provider (ISP). Your local (private) IP address, something like 192.168.1.23, is assigned by your own router and only matters inside your home or office network. This guide covers both.
Dynamic addressing is the default
Almost every consumer internet connection uses dynamic addressing. Rather than permanently assigning each customer a fixed address, the ISP keeps a pool and hands addresses out on request. This lets the provider reuse addresses from customers who are offline, reorganize its network without contacting anyone, and reserve fixed addresses for business plans. Our guide to static vs dynamic IP addresses compares the two models in detail.
Dynamic does not necessarily mean "changes often". Many cable and fiber customers keep the same public IP for months, because the ISP's systems prefer to give a returning device the address it had before. Others see a new address every day. The behavior depends entirely on how your provider has configured its network.
Why your public IP address changes
DHCP lease expiry and renewal
On most cable and fiber networks, your modem or router obtains its public address through DHCP (Dynamic Host Configuration Protocol). The address is a lease with an expiry time. Your router normally renews the lease halfway through, and while it keeps renewing, it usually keeps the same address. If the router is switched off long enough for the lease to lapse, the ISP may give that address to someone else, and you get a new one when you come back online.
Router or modem restarts
Restarting your equipment does not always change your IP, but it often can. When the router reconnects it requests a fresh lease, and whether you get the old address back depends on the ISP. Replacing the router has a bigger effect: DHCP servers commonly identify clients by their MAC address, so a new router looks like a new customer and frequently receives a different IP.
PPPoE sessions
Many DSL and some fiber connections use PPPoE, where the router logs in with a username and password. On these networks a new address is typically assigned every time the session is re-established, after a restart, a line drop or a scheduled disconnect. Some ISPs deliberately end sessions periodically, which produces a new IP on a regular schedule.
ISP network changes
Providers renumber their networks, move customers between equipment, or swap address blocks between regions. When that happens your address changes even though nothing changed at home. This is also a common reason why the location shown for your IP suddenly jumps to a different city.
Mobile data
Phones and mobile hotspots get a new public IP address very frequently, often whenever the data connection is re-established, such as after airplane mode, a reboot or a long period of inactivity. Mobile carriers also put many customers behind carrier-grade NAT (CGNAT), so the public address you see is shared with other subscribers and is drawn from a pool that can change between connections.
VPNs, proxies and private relays
Connecting to a VPN replaces your visible IP with one belonging to the VPN server. Switching servers, reconnecting or letting the VPN app pick the "fastest" location will all change the address websites see. Services like iCloud Private Relay rotate addresses as well. If your IP looks unfamiliar, check whether a VPN or relay is active before assuming anything else.
Switching networks
Your IP belongs to the network you are connected to, not to your device. Moving from home Wi-Fi to mobile data, to an office network or to a café hotspot gives you a completely different public address each time.
IPv6 addresses change on purpose
If your connection supports IPv6, you may notice your IPv6 address changing even more often than your IPv4 address. That is usually by design. Modern operating systems use temporary privacy addresses (defined in RFC 8981, which replaced RFC 4941): the device generates a random interface identifier for outgoing connections and replaces it periodically, typically about once a day, so websites cannot track a device by a permanent address.
On top of that, some ISPs change the IPv6 prefix they delegate to your router after a reconnect, which changes the first half of every address in your home. Because of both mechanisms, a changing IPv6 address is rarely a sign of a problem.
Why your local IP address changes
Inside your network, your router runs its own DHCP server and leases private addresses to your devices. A device's local IP can change when:
- The lease expires while the device is away, and the router assigns the address to something else.
- The router is reset or replaced, and its DHCP pool or subnet changes, for example from
192.168.0.xto192.168.1.x. - The device uses a private or randomized MAC address for Wi-Fi. iPhones, Android phones, Windows and macOS can present a different MAC address per network, or rotate it over time, so the router sees what looks like a new device. See our guide to MAC addresses for how this works.
Local IP changes matter when you have set up port forwarding, a network printer or a home server that other devices reach by address. The fix is a DHCP reservation: in your router's settings, bind a fixed IP to the device's MAC address. If the device uses a private Wi-Fi address, either reserve that address or turn the feature off for your home network so the MAC stays constant.
How to check whether your IP has changed
- Open the ToolsForAnyone homepage and note your public IPv4 and IPv6 addresses.
- Check them again later, or after a router restart, and compare.
- Use What is my ISP to confirm which provider and network the address belongs to. If the ISP name is a VPN or hosting company, a VPN or proxy is active.
- For your local address, run
ipconfigon Windows oripconfig getifaddr en0on macOS, or check the device list in your router.
How to get an IP address that stays the same
| Goal | Option | Notes |
|---|---|---|
| Fixed public IPv4 | Static IP from your ISP | Often only on business plans or as a paid add-on; ask your provider. |
| Reach a home server by name | Dynamic DNS (DDNS) | A small client on your router updates a hostname whenever the IP changes. Does not work behind CGNAT. |
| Fixed address you control | VPN with a dedicated IP | Many VPN providers sell a dedicated address that stays the same across sessions. |
| Remote access without a public IP | Tunnels or mesh VPNs | Outbound tunnel services and mesh VPNs work even when your IP changes or is shared. |
| Stable local IP | DHCP reservation | Set in the router; free and works for any device. |
Frequently asked questions
Is it bad if my IP address changes?
No. A changing IP is normal and has no effect on everyday browsing, streaming or gaming. It only causes problems when something depends on your address, such as a firewall allowlist at work, a self-hosted server or a remote camera reached by IP.
Why does my IP change every time I restart the router?
Your ISP probably uses PPPoE or short DHCP leases and does not try to reassign the previous address. Some providers keep the same address across restarts and others do not; there is no setting on your router that changes this. Only the ISP can give you a fixed address.
Can someone else get my old IP address?
Yes. Once an address returns to the ISP's pool it can be assigned to another customer. This is why IP addresses are a weak way to identify a person over time, and why your new address may already be on a blocklist because of its previous user.
Why does my IP show a different city after it changes?
Geolocation databases map address blocks to places, and different blocks from the same ISP may be registered to different cities or to a central hub. A new address can therefore appear to be somewhere else even though you have not moved.