- DOCSIS 4.0 supports up to 10 Gbps download and 6 Gbps upload speeds, compared to DOCSIS 3.1's 5 Gbps down and 1.5 Gbps up — but consumer-grade DOCSIS 4.0 modems are not yet available for retail purchase as of March 2026.
- DOCSIS 3.1 remains the best choice for most cable internet subscribers right now. It supports multi-gigabit plans and is widely compatible with Xfinity, Spectrum, and Cox.
- If your ISP has not rolled out DOCSIS 4.0 in your area, there is no reason to wait. A quality DOCSIS 3.1 modem will serve you well for years to come.
What Is DOCSIS and Why Does the Version Matter?
DOCSIS stands for Data Over Cable Service Interface Specification. It is the technology standard that allows your cable modem to send and receive internet data over the coaxial cable coming into your home. Every cable modem uses a version of DOCSIS, and the version determines the maximum speeds your modem can handle.
Think of DOCSIS like a highway. Older versions have fewer lanes and lower speed limits. Newer versions add more lanes and raise the speed limit. If your modem uses an older DOCSIS version than what your internet plan requires, you will not get the speeds you are paying for — even if your ISP's network supports them.
DOCSIS 3.1 vs DOCSIS 4.0: What Are the Differences?
The jump from DOCSIS 3.1 to DOCSIS 4.0 is significant, but the differences are easier to understand than you might think.
Speed
DOCSIS 3.1 supports theoretical maximum speeds of up to 5 Gbps download and 1.5 Gbps upload. In practice, most DOCSIS 3.1 modems on the market support plans up to 2.5 Gbps downstream.
DOCSIS 4.0 raises the ceiling to 10 Gbps download and 6 Gbps upload. The upload improvement is the headline feature — it is a fourfold increase in upstream capacity that makes cable internet competitive with fiber for the first time.
Upload Performance
This is where DOCSIS 4.0 makes the biggest real-world difference. DOCSIS 3.1 was designed in an era when most internet activity was download-heavy (streaming, browsing, downloading files). Upload speeds were an afterthought.
Today, video conferencing, cloud backups, live streaming, and working from home all depend heavily on upload speed. DOCSIS 4.0 was built with these use cases in mind, enabling true symmetrical speeds (meaning your upload speed can match your download speed) over existing cable lines.
Latency
DOCSIS 4.0 includes improved low-latency features that reduce lag during online gaming, video calls, and other real-time activities. While DOCSIS 3.1 also supports Active Queue Management (AQM) for latency reduction, DOCSIS 4.0 builds on this with more advanced capabilities.
Technology Under the Hood
DOCSIS 4.0 comes in two flavors that ISPs can choose from: Full Duplex (FDX), which allows upload and download traffic to share the same spectrum, and Extended Spectrum DOCSIS (ESD), which expands the total available spectrum to 1.8 GHz. Comcast uses FDX, while Charter (Spectrum) is pursuing ESD. As a consumer, you do not need to worry about which one your ISP uses — either approach delivers the same speed improvements to your home.
Where Is DOCSIS 4.0 Available Right Now?
As of March 2026, DOCSIS 4.0 deployment is still in its early stages. Here is the current status of major ISPs:
Comcast (Xfinity) is the clear leader. Comcast launched the world's first commercial DOCSIS 4.0 service in late 2023 and has expanded to more than ten U.S. markets, including Atlanta, Philadelphia, Denver, Seattle, Miami, Sacramento, Pittsburgh, and Colorado Springs. Their X-Class Internet plans offer symmetrical speeds up to 2 Gbps, with 3 Gbps and 5 Gbps tiers expected to follow.
Charter (Spectrum) has completed initial network upgrades across roughly 15% of its footprint. Full DOCSIS 4.0 deployment was originally targeted for 2025 but has been pushed to 2026 due to equipment certification delays.
Mediacom launched commercial DOCSIS 4.0 service in select markets starting in September 2025.
Cox, Midco, and others are expected to follow as equipment reaches volume production, but no firm consumer launch dates have been announced.
Can You Buy a DOCSIS 4.0 Modem Yet?
No. As of March 2026, there are no consumer DOCSIS 4.0 modems available for retail purchase through Amazon, Best Buy, or other retailers. The DOCSIS 4.0 modems currently in use are ISP-provided equipment — for example, Comcast supplies its own proprietary gateways (like the XB10) to X-Class Internet subscribers.
Manufacturers like Hitron have announced DOCSIS 4.0 hardware (such as the CODA60), but these are designed for operator deployment, not direct consumer purchase. Industry analysts expect retail DOCSIS 4.0 modems from brands like ARRIS/Motorola, NETGEAR, and Hitron to begin appearing on store shelves in mid-to-late 2026.
Should You Upgrade From DOCSIS 3.1 to DOCSIS 4.0 in 2026?
For the vast majority of cable internet subscribers, the answer is: not yet. Here is why.
First, you cannot buy a DOCSIS 4.0 modem at retail right now. If your ISP has not deployed DOCSIS 4.0 in your area and offered you their equipment, the option simply does not exist.
Second, DOCSIS 3.1 handles everything most households need. If you are on a plan of 1 Gbps or even 2.5 Gbps, a good DOCSIS 3.1 modem with a 2.5 GbE Ethernet port will deliver those speeds without any issues.
Third, even in areas where DOCSIS 4.0 is live, the plans currently top out at 2 Gbps symmetrical — speeds that are impressive but not dramatically different from what high-end DOCSIS 3.1 setups can deliver on the download side.
When It Makes Sense to Upgrade
You should consider DOCSIS 4.0 when all three of these conditions are true:
1. Your ISP has deployed DOCSIS 4.0 in your neighborhood.
2. Retail DOCSIS 4.0 modems are available (or your ISP offers a gateway you are comfortable using).
3. You need significantly faster upload speeds for activities like video conferencing, live streaming, or large cloud backups.
When You Should Stick With DOCSIS 3.1
If you are on a plan of 1 Gbps or less, a DOCSIS 3.1 modem is more than capable. If your ISP has not rolled out DOCSIS 4.0 locally, upgrading your modem would make no difference. And if your current DOCSIS 3.1 modem is working well, there is simply no urgency to replace it.
Best DOCSIS 3.1 Modems to Buy Right Now
Until DOCSIS 4.0 modems hit retail shelves, these are the most reliable DOCSIS 3.1 modems available in 2026. All support plans up to 2.5 Gbps and include a 2.5 GbE Ethernet port:
ARRIS S33 — Widely considered the gold standard for standalone cable modems. Stable Broadcom chipset, no built-in Wi-Fi (pair with your own router). Compatible with Xfinity, Spectrum, and Cox.
Motorola MB8611 — Another excellent standalone option with strong performance and broad ISP compatibility.
NETGEAR CM2000 — A solid DOCSIS 3.1 modem with multi-gig support, compatible with most major cable ISPs.
Hitron CODA56 — A reliable modem built for speed and wide ISP compatibility, with a 2.5 GbE port.
DOCSIS 3.1 vs DOCSIS 4.0: Quick Comparison
| Feature | DOCSIS 3.1 | DOCSIS 4.0 |
|---|---|---|
| Max Download Speed | 5 Gbps | 10 Gbps |
| Max Upload Speed | 1.5 Gbps | 6 Gbps |
| Symmetrical Speeds | No | Yes |
| Low Latency Features | Basic (AQM) | Advanced |
| Retail Modems Available | Yes, widely available | Not yet (expected mid-to-late 2026) |
| ISP Deployment | Nationwide | Limited markets only |
| Backward Compatible | Yes (with DOCSIS 3.0) | Yes (with DOCSIS 3.1 and 3.0) |
Frequently Asked Questions
Is DOCSIS 4.0 worth the upgrade over DOCSIS 3.1?
For most people, not yet. DOCSIS 4.0 offers major upload speed improvements and lower latency, but retail modems are not available and ISP deployment is limited. If your DOCSIS 3.1 modem is working well and meets your plan speed, there is no need to upgrade today.
Will my DOCSIS 3.1 modem still work when my ISP upgrades to DOCSIS 4.0?
Yes. DOCSIS is backward compatible, so your DOCSIS 3.1 modem will continue to work on a DOCSIS 4.0 network. However, you will not benefit from the higher upload speeds or other DOCSIS 4.0 improvements until you replace your modem with a DOCSIS 4.0 model.
When will DOCSIS 4.0 modems be available to buy?
Industry analysts expect consumer DOCSIS 4.0 modems from brands like ARRIS, Motorola, NETGEAR, and Hitron to begin appearing at retailers in mid-to-late 2026. As of March 2026, no retail DOCSIS 4.0 modems are available on Amazon or Best Buy.
Which ISPs support DOCSIS 4.0 right now?
Comcast (Xfinity) is the furthest along, with commercial DOCSIS 4.0 service in more than ten U.S. markets. Mediacom has launched in select markets. Charter (Spectrum) is upgrading its network but has not broadly deployed DOCSIS 4.0 to consumers yet. Cox and other providers are expected to follow later.
Does DOCSIS 4.0 make cable internet as fast as fiber?
DOCSIS 4.0 closes the gap significantly. With support for symmetrical multi-gigabit speeds, it matches what many fiber providers offer at the consumer level. However, fiber still has inherent advantages in consistency and latency over very long distances. For most home users, DOCSIS 4.0 performance will be virtually indistinguishable from fiber.
Do I need a new router to use DOCSIS 4.0?
If you plan to take full advantage of DOCSIS 4.0 multi-gigabit speeds, you will want a router that supports Wi-Fi 6E or Wi-Fi 7 and has a 2.5 GbE or 10 GbE WAN port. A standard Wi-Fi 5 or Wi-Fi 6 router with a 1 Gbps Ethernet port would bottleneck your connection.
Should I buy a DOCSIS 3.1 modem now or wait for DOCSIS 4.0?
If you need a modem today, buy a DOCSIS 3.1 modem. There is no reason to wait for a product that is not yet available at retail. A quality DOCSIS 3.1 modem like the ARRIS S33 or Motorola MB8611 will serve you well for years, and you can upgrade to DOCSIS 4.0 later when the modems and ISP support are both in place.
