Short answer
Yes, a router will power on and work without a modem, but it will not have internet access on its own. A router shares a connection; it does not create one. For most home internet types you need something that connects to your provider’s line, and that is the modem’s job.
What a router can do on its own
Without any internet source, a router can still run a local network. Devices connected to it can:
- Share files with each other
- Print to a networked printer
- Talk to smart home gadgets that work locally
- Play local network games that don’t need online servers
None of this reaches the wider internet. Our article on what a wireless router can still do without internet goes into more detail.
Why internet usually needs a modem
Your provider delivers service over cable, DSL or fiber lines. A modem (or, for fiber, an ONT) converts that signal into standard Ethernet data. The router’s internet port expects that Ethernet data. If nothing supplies it, the router has nothing to share. For a broader comparison, see gateway vs router.
Cases where you don’t need a separate modem
- Fiber with an ONT: the ONT does the modem’s job, so you plug your router into it. See what an ONT is.
- Building or landlord Ethernet: some apartments, offices and campuses supply internet through an Ethernet wall jack. A router can plug in there. See how to connect a wireless router without a modem.
- A modem/router combo already installed: the modem is built in, so you may add your own router behind it. See using a router with a modem/router combo.
What happens if you plug a new router in anyway
If you connect a new router to a wall jack that carries no usable internet signal, its lights will typically show that it has no internet connection, and devices may join its Wi-Fi but be unable to load websites. Nothing is damaged by this; you are just missing the piece that talks to your provider.
How to tell which situation you’re in
- Look at what comes into your home: a coax cable (cable internet), a phone line (DSL), a fiber cable going to a box (fiber), or an Ethernet jack.
- Check whether the box your provider gave you already includes Wi-Fi. If it does, it may already be a modem and router in one.
- If unsure, ask your provider which equipment you need.
FAQ
Can you just buy a router for WiFi? Only if something else already delivers internet to it, such as an ONT, a modem or an active Ethernet jack.
Do you just plug in a new router? It depends on the setup. You plug it into the modem, ONT or Ethernet source, power it on, then complete its setup, which usually includes a Wi-Fi name and password.
How can I set up a router without a modem? For a local network, power it on and connect devices. For internet, you need one of the sources above.