Guide
Why does my IP address keep changing?
DHCP leases, router reboots, ISP maintenance and mobile churn — the full list of reasons your IP changes, how often each network type does it, and when you actually need a fixed address.
On this page
The DHCP lease model
Your ISP does not sell you an address; it lends one. When your router connects, the provider hands it an address from a pool for a limited time — a lease — typically anything from a few hours to several days. Renewals happen automatically, but when a lease lapses or the router reconnects, the provider may hand out a different address from the pool. That is the whole mechanism behind "my IP changed overnight".
What triggers a change
- Router or modem restart — the most common cause at home: power cut, firmware update, a curious family member.
- Lease expiry — on shorter-lease providers this can mean a fresh address every day or two.
- ISP maintenance or failover — when your connection briefly drops between access lines or cabinets, it often comes back on a new address.
- Provider policy — some mobile and budget providers deliberately churn addresses frequently.
If you want to see the mechanics from the other side, what an IP address is covers how the pool is allocated to your ISP in the first place.
Mobile networks change it faster
Mobile data re-negotiates far more aggressively — on reconnect, when you move between towers, or when the carrier's session timers expire. Many mobile networks also run CGNAT, adding another layer of re-shuffling. Net effect: a phone's public IP can change several times a day, while a home broadband line may sit on the same address for weeks.
| Network type | Typical address lifetime |
|---|---|
| Home broadband (dynamic) | Hours to weeks |
| Business line with fixed IP | Until you ask to change it |
| Mobile (4G/5G) | Minutes to hours |
| CGNAT line | Unpredictable — the carrier decides |
When you need it to stay still
For everyday browsing, changing IPs are a feature, not a bug — they make correlation between your old and new connections harder. A stable address only matters if you host something (a web app, mail server, VPN endpoint), allowlist your IP in a service, or need a fixed remote-access path. In those cases the options are a static IP, a dynamic-DNS hostname that follows your changing address, or a small cloud server with a fixed address in front of your home.
Frequently asked questions
Do websites see my old IPs when the address changes?
They see the IP on each request, so yes — but each site only sees what it sees; no site is handed a history of your previous addresses. Your ISP keeps the allocation logs, subject to its retention policy and legal process.
Why does my neighbour's IP never change?
Probably a static (fixed) address on a business plan, or a very long DHCP lease with a small provider pool.
Can I force my ISP to keep the same IP?
Yes, by requesting a static address — usually a business option or a paid upgrade — or by keeping the router powered on so the lease never lapses, which is unreliable in practice.
Keep reading
- What is an IP address?
- Public vs private IP addresses
- IPv4 vs IPv6
- How to hide your IP address
- How to check your IP address on a phone
- What is CGNAT?
- How to change your IP address
- How to find a website's IP address
- What is a datacenter IP?
- IPv6 privacy extensions
- What is an ASN?
- How IP geolocation works
- What is a local IP address?
- Why am I getting blocked or stuck on CAPTCHAs?
- What is IP reputation?
- How websites detect VPNs and proxies
- What is a DNS leak?
- What is a WebRTC leak?
- Proxy vs VPN
- How to check if your VPN actually works
- Static vs dynamic public IP
- How to find out who owns an IP address
- IPv6 in 2026
- Check my public IP address
Check any other IP address
Investigating a suspicious login, a spam email header or a server log entry? Run any IPv4 or IPv6 address through the same geolocation and proxy checks.