Static or dynamic IP: how to tell which one you have
The question comes up the moment you want to host something at home, and the answer depends less on your hardware than on your subscription.
The difference, in one sentence
A static address stays the same indefinitely. A dynamic address is lent to you by your provider and can be taken back, usually when your router restarts, after a line outage, or during maintenance on the provider's side.
Either way, the address works identically for browsing. The distinction only matters when something needs to reach you: a server hosted at home, remote access to cameras, a VPN tunnel back to your house, or an access rule that filters by address.
How to find out
No command answers this directly: an address carries no marking that reveals its nature. You establish it by observation.
Note your current address on the home page. Then restart your router, wait for it to come back online, and reload the page. If the address changed, you have your answer: it is dynamic.
If it did not change, that proves nothing yet. Many dynamic addresses stay stable for weeks as long as the connection holds. The "Your previous addresses" section on the home page records your readings in your browser: come back in a few days, then in a few weeks. An address unchanged after several restarts and a month of use is static in practice, even if your contract does not guarantee it.
The surest route is still to read your contract or your router's admin interface, which sometimes states the assignment mode outright.
What providers offer
Consumer plans are usually dynamic, business plans usually static and priced accordingly. Some providers offer a static address as a paid option on residential plans. A few include one by default, which makes them popular with people who self-host.
Always check with your own provider rather than trusting a general rule: offers change, and the same brand can use both modes depending on the plan.
The special case of shared addresses
There is a third situation, increasingly common, that surprises many people: carrier-grade NAT. Your connection then has no public address of its own; you share one with several hundred other subscribers.
This is standard on mobile connections and 4G or 5G routers, and it exists on some fibre plans too. The symptom is clear: the address shown on this page does not match the one in your router's interface, which starts with 100.64 through 100.127.
In that case no port forwarding will work, and the static-or-dynamic question becomes moot: nothing can reach you from outside. Some providers will move you off carrier-grade NAT on request.
If you need a stable address
Asking for a static IP is not always the right reflex. A dynamic DNS service solves the problem in most cases: a small client on your router or NAS reports your current address to a service that keeps a hostname up to date. You reach your home by that name, without caring which address sits behind it.
Most NAS units and routers include this feature. It fails only under carrier-grade NAT, where the problem is not an unstable address but the absence of one.