Static vs dynamic IP addresses: which one do you have?

Does your IP address ever change? For most people the honest answer is: yes, occasionally, and usually without you noticing. Whether your public IP stays fixed or changes over time comes down to one distinction. A static IP is permanently assigned to you and never changes. A dynamic IP is borrowed from a pool and can be replaced whenever your provider decides. Almost every home connection uses the dynamic kind, and for good reason - but there are real situations where a static address is worth having.

How ISPs hand out addresses: DHCP leases

When your router connects to your internet provider, it does not come with an address of its own. It asks the ISP's network for one, and the ISP responds through a protocol called DHCP (Dynamic Host Configuration Protocol). The address it hands over is not a gift but a lease: it comes with an expiry time, often somewhere between a few hours and several days.

Before the lease expires, your router quietly asks to renew it. If the ISP agrees - which it usually does while you stay online - you keep the same address, sometimes for months. This is why many people believe they have a static IP when they actually have a dynamic one that simply has not changed in a while. The address is likely to change when your router is offline long enough for the lease to lapse, when the ISP does maintenance or reorganizes its network, or when you replace your router and the ISP sees new hardware asking for an address.

Why most homes get dynamic IPs

From the provider's point of view, dynamic addressing is simply more efficient. IPv4 addresses are a scarce resource - the global supply was exhausted years ago - and a pool of leased addresses can serve more customers than a fixed one-to-one assignment, because not everyone is online at once and addresses can be reclaimed and reused. Dynamic pools are also easier to manage: the ISP can renumber parts of its network without coordinating with every affected customer. Static addresses require record-keeping and support overhead, which is why providers typically reserve them for business plans or charge a monthly fee.

CGNAT: when you do not even get your own dynamic IP

Address scarcity has pushed many providers - especially mobile carriers and newer fiber ISPs - one step further, to Carrier-Grade NAT (CGNAT). With CGNAT, you do not get a public IP to yourself at all, even temporarily. Instead, dozens or hundreds of customers share one public address, and the ISP translates between them the same way your home router translates between your devices (we explain that mechanism in local vs public IP).

A quick way to spot CGNAT: check the address your router reports on its WAN or internet status page, then compare it with the public IP shown on our homepage. If they differ - particularly if the router shows an address starting with 100.64. through 100.127. - you are behind CGNAT. In that case port forwarding will not work no matter how you configure your own router, since the sharing happens upstream at the ISP.

Static vs dynamic at a glance

Who actually needs a static IP?

Fewer people than you might think. A static address matters when something on the internet needs to find you reliably, rather than the other way around:

• Self-hosting: running a website, game server or home lab that others connect to by address. A stable IP means DNS records and bookmarks never break.
• Remote access: reaching a home NAS, security cameras or a Raspberry Pi while travelling, without wondering whether the address changed since you left.
• Some VPN and firewall setups: site-to-site VPNs between offices often require fixed endpoints, and some corporate networks only allow connections from an approved list of IP addresses.
• Mail servers: the strongest case of all. Spam filters distrust mail from dynamic ranges, and reverse DNS - which providers only configure for static addresses - is effectively mandatory for deliverability.

If none of these apply to you, a dynamic IP has no practical downside. Browsing, streaming, gaming and video calls all initiate connections outward, and it makes no difference whether your address changed last night.

The cheap alternative: dynamic DNS

If you only want to reach your own equipment from outside, you can get most of the benefit of a static IP for free with dynamic DNS (DDNS). The idea is simple: instead of remembering an address that keeps changing, you use a hostname such as myhome.example.net, and a small piece of software keeps that hostname pointed at your current IP.

In practice it works like this: you create an account with a DDNS provider (many routers have built-in support for popular ones, and several offer free tiers), pick a hostname, and enable the update client in your router's settings. From then on, whenever your ISP hands you a new address, the router reports it and the hostname is updated within a minute or two. You connect to the name, not the number, so the changes stop mattering. The only gap is the brief window between an address change and the next update - fine for personal use, less acceptable for a production service. Note that DDNS does not help behind CGNAT, since the hostname would point at an address shared with hundreds of strangers.

How to check whether your IP has changed

There is no setting on your computer that reveals this - your public address lives at the ISP level. The straightforward method is to check what your current public IP is, note it down, and compare again after a router reboot or a few days later. If the address is identical for weeks across reboots, you may have a static assignment or a very generous lease; if it shifts, you know you are dynamic and can plan accordingly.

Getting a static IP from your ISP

If you decide you need one, the path is usually short: contact your provider and ask for a static, public IPv4 address. Expect a small monthly fee on consumer plans, or the requirement to move to a business subscription. Two things are worth confirming before you pay. First, that the address is genuinely public and routable, not a fixed address behind CGNAT - some providers market the latter, and it will not help with hosting. Second, if you plan to run a mail server, ask whether they will set up reverse DNS for your address.

One last note on privacy: a static IP is a permanent identifier, which makes it marginally easier for websites and trackers to recognize you over time. If that trade-off bothers you, read about your options in how to hide your IP address.