The USB Cable Primer
Everything you need to know about USB cables, without the technical jargon.
Why USB-C is Chaos
USB-C was supposed to be the "one cable to rule them all." Instead, it created a new kind of confusion: cables that look identical but have wildly different capabilities.
The same USB-C cable might transfer data at 480 Mbps or 40,000 Mbps. It might charge at 5W or 240W. It might support video output or not. And you can't tell by looking at it.
This happens because USB-C is just a connector shape. The actual capabilities depend on:
- The protocol the cable supports (USB 2.0, USB 3.2, USB4, Thunderbolt)
- The power delivery rating of the cable
- Whether the cable has the wiring for video signals
- The quality of the cable construction
A $5 cable and a $50 cable will both fit the same port. Only one will actually work for what you need.
What the Version Numbers Mean
| Name | Speed | What It's Good For |
|---|---|---|
| USB 2.0 | 480 Mbps | Charging, keyboards, mice. Not for data transfer. |
| USB 3.2 Gen 1 | 5 Gbps | External drives, most peripherals. |
| USB 3.2 Gen 2 | 10 Gbps | Fast external SSDs. |
| USB4 | 20-40 Gbps | High-speed storage, docks, displays. |
| Thunderbolt 4 | 40 Gbps | Pro displays, eGPUs, high-end docks. |
The naming is a mess on purpose. USB 3.0 became USB 3.1 Gen 1, which became USB 3.2 Gen 1. Same speed, three names. The USB-IF keeps renaming old standards to make new ones sound better.
Understanding Power Delivery
"USB Power Delivery" (USB PD) is a separate standard from data speed. A cable can be fast for data but slow for charging, or vice versa.
Standard USB
5W - 15W
Enough for phones (slowly)
USB PD (older cables)
Up to 100W
Most laptops, fast phone charging
USB PD 3.1 (EPR)
Up to 240W
Gaming laptops, high-power devices
Watch Out
Cheap cables may only support 5W even if your charger outputs 100W. The cable is the bottleneck.
How to Read Cable Packaging
When shopping for USB cables, look for these key specs:
Data Speed Rating
Look for "5 Gbps", "10 Gbps", "40 Gbps", or version numbers like "USB 3.2 Gen 2"
Power Rating
Listed in watts (W). "60W", "100W", or "240W". Higher is better for charging.
Video Support
Look for "DisplayPort Alt Mode", "HDMI Alt Mode", or "Video-enabled". Not all cables have this.
Certification Logos
USB-IF certified (trident logo), Thunderbolt (lightning bolt). These mean tested and verified.
The Simple Rule
If the packaging doesn't clearly state the speed and power ratings, assume the worst. Quality cables always advertise their capabilities.
Quick Tips
- 1. For charging only: Any cable works, but check the wattage rating if you want fast charging.
- 2. For external drives: Get at least USB 3.2 Gen 1 (5 Gbps). USB 2.0 will bottleneck your SSD.
- 3. For monitors/docks: You need a video-capable cable. Look for Thunderbolt or "DP Alt Mode".
- 4. Shorter is better: Longer cables often can't maintain top speeds. Stick to 1-2 meters for USB4/Thunderbolt.
- 5. When in doubt, check the logo: Thunderbolt (lightning bolt) cables do everything. They're expensive but foolproof.
Not Sure What Connector You Have?
Use our visual identifier to figure out which USB connector you're looking at.
Identify My Connector