What Is a Modem?
A modem (short for modulator-demodulator) is the device that connects your home to your internet service provider. It translates the signal from your ISP (whether cable, DSL, fiber, or fixed wireless) into a digital signal that your home network can use. Think of the modem as the bridge between the internet and your home.
Without a modem, your devices cannot access the internet. The modem connects to an incoming cable (coaxial for cable internet, phone line for DSL, fiber-optic cable for fiber) on one side and to your router (or directly to a computer) via Ethernet cable on the other side.
What Is a Router?
A router creates your home network and distributes the internet connection from the modem to all your devices, both wired (via Ethernet ports) and wireless (via WiFi). The router assigns each device a local IP address, manages traffic between devices, and provides security features like a firewall and network encryption.
Without a router, only one device could connect to the internet at a time via a direct Ethernet connection to the modem. The router is what allows your phone, laptop, smart TV, gaming console, and dozens of smart home devices to all share the same internet connection simultaneously.
Modem vs Router: Key Differences
- Function: The modem connects to your ISP and translates the signal. The router distributes that connection to your devices.
- Connection: The modem connects to the outside (ISP cable or phone line). The router connects to the modem and to your devices.
- WiFi: Modems do not provide WiFi. Routers create the wireless network.
- Number needed: You need one modem and one router (or one combo device).
- ISP-specific: Modems must be compatible with your ISP type (cable, DSL, fiber). Routers work with any ISP.
What About Gateway Devices?
Many ISPs provide a gateway, which is a modem and router combined into a single device. Gateways are convenient because they reduce the number of devices and cables, but they have drawbacks. Gateway devices often deliver worse WiFi performance than dedicated routers, limit your ability to customize network settings, and come with a monthly rental fee of $10 to $15.
For the best performance and long-term savings, most networking experts recommend using a separate modem and router. This gives you the flexibility to upgrade each component independently and eliminates the monthly rental fee.
Choosing the Right Modem
When buying a modem, match it to your ISP type:
- Cable internet: Get a DOCSIS 3.1 modem. It supports speeds up to 10 Gbps and is backward-compatible with DOCSIS 3.0 networks. Popular options include the Motorola MB8611 and ARRIS SURFboard SB8200. Expect to pay $80 to $150.
- DSL: Get a DSL modem compatible with your provider (ADSL or VDSL). Options are more limited. The Actiontec C3000A is a reliable choice.
- Fiber: Fiber providers typically supply an ONT (Optical Network Terminal) at no extra charge. You cannot replace it with a third-party device. You only need a router.
Choosing the Right Router
Router features to prioritize:
- WiFi standard: WiFi 6 (802.11ax) minimum for 2026. WiFi 6E adds the 6 GHz band for less congestion.
- Speed rating: Match or exceed your internet plan speed. An AX3000 router handles plans up to 300 Mbps; AX5400 handles up to 1 Gbps.
- Coverage: Single routers cover up to 1,500 to 2,500 square feet. For larger homes, get a mesh system.
- Ethernet ports: At least 4 gigabit Ethernet ports for wired devices. Some premium routers offer 2.5 Gbps or 10 Gbps ports.
- Price range: $60 to $100 for solid single routers; $200 to $400 for mesh systems covering 3,000+ square feet.
Do I need both a modem and a router?
For cable and DSL internet, yes, you need both (or a combo gateway device). For fiber internet, you only need a router because the provider installs an ONT that functions as the modem. For 5G home internet, the provider gateway handles both functions.
Should I rent equipment from my ISP or buy my own?
Buying your own saves $120 to $180 per year in rental fees. A modem costs $80 to $150 and a good router costs $60 to $150, so you break even in about 12 months. Check your ISP compatible equipment list before purchasing. Note that fiber internet ONTs are always provided by the ISP.
Can I use any router with any ISP?
Yes. Routers are universal. They connect to your modem via an Ethernet cable and work with any internet provider. The modem is the ISP-specific device. When you switch ISPs, you may need a new modem but can keep the same router.