Best Cable Modems for Xfinity

For most Xfinity customers the modem to buy is the ARRIS SURFboard S33: DOCSIS 3.1, a 2.5 Gbps port, and approval across Xfinity and the other major cable providers. If you are on a plan at or below 1 Gbps and want the money back as fast as possible, buy the Hitron CODA instead. Above a gigabit, step up to the Netgear CM2000.

Xfinity has the largest equipment fee among the major cable providers, which makes buying your own modem the clearest financial win covered on this site — the gateway rental is a charge that never ends, and a modem is a one-time purchase that typically pays for itself inside a year. The catch is that the decision is not really about the modem brand. It is about three things: approval, your speed tier, and whether you also want Wi-Fi in the same box.

Step one: check approval before you order anything

Xfinity will only activate devices it recognizes, and it maintains its own compatibility tool — “My Device Info” — which is the authority on whether a specific model works on your specific plan. Check the model there before you buy, not after it arrives. Xfinity's own guidance is blunt about where the responsibility sits once you own the hardware: you keep the device updated and secure, you use equipment that supports your internet speed, you troubleshoot problems with it, and you manage your own Wi-Fi security. For Gigabit Internet, Xfinity states the device must support Gigabit speeds.

That last sentence is the whole of step two, and it is where people lose money — either by buying a modem too slow for the plan they are on, or by buying three times more modem than the plan can use.

Step two: match the modem to the tier, not to the brand

The port-speed point deserves spelling out because it is the most common waste in this category. Gigabit Ethernet cannot actually deliver a gigabit plan once protocol overheads are counted, so a 1 Gbps plan behind a Gigabit-only modem is capped slightly below what you are paying for. Multi-gig ports explained does the arithmetic. Below about 600 Mbps the point is moot and a Gigabit port is plenty.

Step three: decide whether you want the Wi-Fi in the same box

A modem and a router do different jobs. The modem connects the house to Xfinity; the router shares that connection and provides Wi-Fi. Xfinity rents you a gateway that is both. You can replace it with one box that is also both, or with two separate boxes.

Separates win on two counts. The modem and the Wi-Fi age at completely different rates — DOCSIS generations last years while Wi-Fi standards turn over every few — and keeping them apart means you can replace the half that has fallen behind. And the modem has to live where the coax enters the building, which is usually a corner, a garage or a utility closet, and a poor place to broadcast from. Separates let the modem stay put while the router goes somewhere sensible. Router vs modem vs gateway sets out the distinction, and modem-router combos: when they make sense argues the trade-off in full.

A combo wins when you want one purchase, one power socket and one support phone call — which is a perfectly reasonable thing to want. The Orbi CBK752 is the version of that we would buy, because it at least adds a mesh satellite rather than asking one box in the utility closet to cover the house.

What you give up by owning the modem

Honesty about the downsides, because they are real and nobody selling you a modem mentions them.

• Support gets simpler for them and harder for you. With a rented gateway, a fault is Xfinity's problem. With your own modem, the first question on every call is whether your equipment is the cause.
• You carry the upgrade risk. If Xfinity retires a DOCSIS generation or your plan outgrows the modem, replacing it is on you. Buying DOCSIS 3.1 rather than an older 3.0 unit is the cheap insurance against the first half of that.
• Some bundles make the fee look smaller. Promotional packages that fold equipment into the price change the payback math. Work out the fee you are actually paying on your current bill before assuming a figure.
• Voice service complicates it. If you take phone service over the same line, check what your own modem does and does not support before you order — this is exactly what the approval tool is for.

Setting it up without a bad afternoon

Check the model in Xfinity's compatibility tool. Order it. Before swapping anything, write down the serial number and MAC address printed on the modem, because activation asks for them. Connect the coax and power, wait for the lights to settle, then activate through the Xfinity app or by phone. Return the rented gateway and keep the receipt — unreturned equipment charges are the most common way this project stops saving money.

Then deal with the Wi-Fi half deliberately rather than by accident. If you bought separates, your new router is the only thing broadcasting and there is nothing to disable. If you kept the gateway for any reason, put it in bridge mode or turn its Wi-Fi off so you are not running two networks in one building — replacing your ISP's router covers the per-provider detail, and our Xfinity page has the provider-specific context on fees and plans.

If you are shopping for the router half at the same time, best home Wi-Fi routers covers the single-box answer and best Wi-Fi 6 mesh systems covers the multi-radio one. If your gateway is rented and you only want to patch one weak room for now, extenders behind a rented ISP gateway explains what will and will not work.

How we picked

We do not run a test lab. Rankings here are built from the manufacturers' published specifications, measurements taken by independent outlets that do have labs, and the structural reasoning on this site about what a given house or job actually needs. Every product was checked as currently sold before it was included. Where a figure appears it is attributed and linked in Sources; where we have no basis for a claim, it is left out. Our methodology sets out exactly what we will and will not assert.