Even USB experts can get tripped up by USB cable names
Here's a frustrating example; imagine you are trying to choose among cables with the following descriptions:
- USB 3.0
- USB 3.1 Gen 1
- USB 3.2 Gen 1
- SuperSpeed USB
- USB 5Gbps
Which one is the fastest? Believe it or not, they all describe the same thing: a 5 Gbps USB-C cable!
The USB implementers forum (USB-IF), a consortium of USB device and cable manufacturers, has tried to address this problem by defining specific marketing terms for each cable speed. Unfortunately, a mix of old and new technical and marketing names are still widely used in product listings and specifications.
Data rates: Changing names over time
USB-C cables are currently sold with five different maximum data rates. To keep track of the various naming conventions, we've put together a table with the old and current USB-IF marketing names and the progression of technical names over time.
| Max Speed | USB-IF Marketing Name(s) | Technical Name(s) | Other Common Names |
|---|---|---|---|
| 480 Mbps | Hi-Speed USB | USB 2.0 | "Fast" |
| 5 Gbps | Old: SuperSpeed USB New: USB 5Gbps | USB 3.0 → 3.1 Gen 1 → 3.2 Gen 1 | USB 3 |
| 10 Gbps → 20 Gbps | Old: SuperSpeed+ → USB 10Gbps New: USB 20Gbps | USB 3.1 Gen 2 → USB 3.2 Gen 2, USB 4 Gen 2 | USB 3.2 Gen 2x2, USB 4 Gen 2x2 |
| 40 Gbps | USB 40Gbps | USB 4 Gen 3 | USB 4 Gen 3x2 |
| 80 Gbps | USB 80Gbps | USB 4 Version 2.0, Gen 4 or dual simplex | USB 4 Gen 4x2 |
So simple! Note that transmission modes, like Gen 2x2 are irrelevant for cables, since valid cables are full featured with all wire pairs present: any "Gen 2" cable is capable of Gen 2x2.
Cable Power Ratings
USB-C cables also vary in the the maximum power they can carry, and the naming is similarly tricky. Here's how the USB-IF defines the power levels for certified cables:
| Marketing Name | Max Voltage | Max Current | Power (W) | Technical Spec | E-Marker Required? | Notes |
|---|---|---|---|---|---|---|
| 60W | 20 V | 3 A | 60 W | USB PD (SPR) | No (≤3A cables) | Most passive USB-C cables without e-marker fall into this category |
| 100W | 20 V | 5 A | 100 W | USB PD (SPR, 5A) | Yes | The previous highest power cable, still common |
| 240W | 48 V | 5 A | 240 W | USB PD 3.1 (EPR) | Yes (EPR-specific) | Must meet stricter safety and signaling rules; labeled “EPR cable” |
- "60W" (20 V, 3 A, no e-marker): Common for charging phones and lower-power laptops
- "100W" (20 V, 5 A, with e-marker): Still widely available; few chargers provide more than 100 W.
- "240W" (48 V, 5 A, with EPR e-marker): Needed for a few high-performance laptops, eGPUs. These cables are constructed similarly to 100W cables with tighter tighter tolerances for insulation and creepage distance.
Why are 100W Cables still Everywhere?
If 240W cables are physically similar to 100W, why hasn't everything moved to 240W?
The short answer is:
- Low demand: few chargers or devices exceed 100 W
- Legacy momentum: 100W cables are already certified and in production
- Certification costs: Recertification to 240W adds cost even if the design is the same
Under the previous USB PD 3.0 (SPR: Standard power range) specification, 100 W (20 V @ 5 A) was the maximum allowed power. USB PD 3.1 (EPR: Extended power range) kept the maximum current at 5 A, but extended voltage to 48 V, allowing for 240 W charging. these cables must meet tighter insulation and creepage requirements and require an updated e-marker chip to indicate EPR support.
SPR 100 W cables can still be certified as compliant under USB PD 3.0, though, in practice, these cables are often uncertified. For new cable designs, the incremental cost of meeting the 240W requirement is lower, and we're seeing 240W cable prices drop as more of the new cables hit the market.
What about the sketchy "15 W USB-C Cables"?
Some popular cables are described as USB-IF certified but support 15 W (5 V, 3 A) only. This is concerning, since:
- 15 W isn't a USB-IF certifiable power level
- USB PD sinks and sources could apply up to 20 V at 3 A (60 W) to the cable
- Unlabeled cables would be easy to accidentally plug into > 5 V
While it's unclear whether these cables are just mislabeled, or if they are actually dangerous, it's best to avoid any cable rated less than 60 W
Passive Cable Length Limits
USB 2.0 cables can be up to 5 meters long - this is specified directly in the standard. USB 3.x and USB4 use an electrical specification: approved cables of any length must meet requirements for signal integrity. Maximum cable length therefore varies with the quality of the cable and speed required. Faster data rates need shorter cables. For commonly available certified cables, this roughly translates to:
| Marketing Name | Approximate Max Cable Length |
|---|---|
| USB 2.0 | 5 m |
| USB 5Gbps | 2 - 3 m |
| USB 20Gbps | 1 m |
| USB 40Gbps | 0.8 - 1 m |
| USB 80Gbps | < 0.8 m |
Note that there are a few USB-IF approved cables that exceed these lengths. For example, 1.5 m USB 80Gbps, and 2 m USB 20Gbps cables from brands like Belkin and CableMatters are about double the nominal lengths. Longer runs will require active cables or USB Extenders.
DisplayPort Alt Mode support
DisplayPort Alt Mode lets a USB-C cable carry video, often while also delivering power and USB Data. It works by reusing two or all four SuperSpeed lanes for DisplayPort Signaling.
For 4K60 video, look for:
- At least 10Gbps cables
- Specific mention of DisplayPort support at 4K60
What about Thunderbolt cables?
Thunderbolt and USB started as independent standards, but over time have converged on protocols and USB-C connectors. USB 4 specifies several optional features that Thunderbolt requires. Think of modern Thunderbolt (especially Thunderbolt 4 and 5) as a more stringent, Intel-certified implementation of USB4, with guaranteed support of features that are optional under USB4.
| Feature / Requirement | USB4 Cables | Thunderbolt 3 Cable | Thunderbolt 4 Cable | Thunderbolt 5 Cable |
|---|---|---|---|---|
| Max Data Rate | 20, 40, 80 Gbps | 20 Gbps (>0.5 m) 40 Gbps (≤0.5 m) | 40 Gbps (all lengths) | 80 Gbps (bidirectional), 120 / 40 Gbps (split mode) |
| Power Delivery Support | 60 / 100 / 240 W (EPR) | Up to 100 W | Minimum 100 W 240 W optional | 140 W required 240 W optional |
| E-Marker Required | Yes if > 3 A or USB3+ | Yes | ||
| USB 3.x Support | Yes | Passive: Yes Active: Maybe | Yes | Yes |
| Certification Body | USB-IF | Intel (Thunderbolt Certified) | ||
| Passive Cable Length (typical) | ~0.8 - 1 m for 20-80 Gbps | ~0.5 m (40 Gbps) ~2 m (20 Gbps) | Up to 2 m (40 Gbps passive or active) | 1 m passive at 80 Gbps |
| Active Cable Limitations | May limit DP or PCIe support | Often without USB 3.x support (USB 2.0-only) | Full compatibility | Full compatibility |
For many applications, the same-spec USB4 or Thunderbolt 4 / 5 cables can be used interchangeably. If using Thunderbolt devices, especially if PCIe or DisplayPort is required, a Thunderbolt-certified cable is the best bet.
Note that a Thunderbolt 3 cable can not be used to put Macs into DFU restore mode.
How to Choose the Right Cable
Start with what you need:
- Mostly charging, no DisplayPort support needed?
- Consider USB 2 cables, since they have the fewest data lines, leaving more space for power, and can be more flexible. Data rate is limited to 480 mbps, but this is often adequate for phone syncing. Many phones, such as the iPhone 15, are USB 2 only.
- Choose a power level that matches the supply or device
- Charging + Display?
- Confirm that your desired resolution and frame rate is explicitly specified for the cable. Choose at least 10Gbps cables for 4K60 to allow USB 5Gbps data over two lanes.
- Match the cable power rating to the display's output. Many monitors provide USB-PD between 60 and 100 W.
- Data-intensive applications?
- For SSDs or USB-to-10GbE adapters, choose based on actual port and device capabilities.
- Longer cable runs?
- If longer cables are needed, you may need to accept a lower data rate, switch to an active cable, or use a USB Exender.
Cable Quality
How do you know if a cable is of good quality?
- Look for USB-IF certified cables from known brands and order from trusted retailers.
- Check certification with the USB-IF certification lookup tool: https://www.usb.org/products
- Note that, some brands rely on the OEM to certify. For example, many AmazonBasics cables are manufactured by CE link and use their certification.
For cables with e-marker chip, devices like our USBHub3c can read the Vendor and Product ID (VID / PID). Certified cables will use registered values. Low-cost uncertified cables will often use dummy values for VID / PID, while knockoffs may use fake or stolen VIDs.
Summary
USB cable naming is chaotic, but manageable. Focus on:
- Data rate
- Power capacity
- Certification status
Use the above tables to decode product specs, and always buy from legitimate vendors and known brands or manufacturers.
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