Short answer: DOCSIS 4.0 mainly raises cable internet’s upload ceiling, from 1 Gbps to 6 Gbps according to CableLabs, which develops the standard. That makes symmetrical multi-gig plans possible over cable. It only matters if your provider offers DOCSIS 4.0 service where you live and you want such a plan. Otherwise a current DOCSIS 3.1 modem is still the right buy, and that’s what’s on retail shelves.
Side by side
| DOCSIS 3.1 | DOCSIS 4.0 | |
|---|---|---|
| Downstream capacity | Up to 10 Gbps | Up to 10 Gbps |
| Upstream capacity | Up to 1 Gbps | Up to 6 Gbps |
| What it enables | Gigabit and multi-gig download plans | Symmetrical multi-gig plans |
| Retail modems | Widely available | None in NETGEAR’s line as of 8 October 2026 |
Capacities are CableLabs’ specification figures; CableLabs notes that real networks vary.
What actually changes: upload
Both versions top out at about the same download capacity. The difference is the other direction: DOCSIS 4.0’s upload ceiling is six times DOCSIS 3.1’s. CableLabs describes how it gets there: full duplex operation (sending and receiving on the same part of the cable spectrum), and extended spectrum up to 1.8 GHz.
Can you buy a DOCSIS 4.0 modem?
Not easily, yet. As of 8 October 2026, NETGEAR’s retail cable modem line was DOCSIS 3.1 only, its top models being the CM3000 and CM2500. Cable providers decide which modems work on their networks: Xfinity, for example, requires an owned modem to work with Xfinity and support your plan’s speed. For a DOCSIS 4.0 plan, expect to use the equipment your provider specifies, at least until retail models reach its approved list.
Will my DOCSIS 3.1 modem stop working?
Not because DOCSIS 4.0 exists. But providers do retire older equipment over time; Xfinity, for instance, won’t install or activate devices it has declared end-of-life. A current DOCSIS 3.1 model, the newest generation in NETGEAR’s retail line, gives you the most time. Check your provider’s list before buying any modem.
Which should you choose?
- On a download-focused cable plan, up to about 2 Gig: a DOCSIS 3.1 modem. The best cable modems list sorts them by plan speed.
- Offered a symmetrical multi-gig plan that needs DOCSIS 4.0: use the provider’s equipment for now. Should you rent or buy your modem and router? covers the trade-offs of renting.
- Not getting the speed you already pay for: a new modem standard probably isn’t the fix; see not getting the internet speed you pay for.