Why some USB-C cables only charge (and don't transfer data)
If you’ve ever plugged a USB-C cable into your phone or laptop and thought “why is it only charging?”, you’re not imagining it. Some USB‑C cables really are charge‑only. Others can transfer data, but only at slow USB 2.0 speeds. Others can do high-speed data, video output, and fast charging.
The frustrating part is that they can all look identical.
The core confusion: USB‑C is the connector, not the capability
USB‑C describes the shape of the plug. But what the cable can actually do depends on the standards and wiring inside:
- Power (charging) is handled via USB Power Delivery (USB‑PD) and the cable’s ability to carry current safely.
- Data is handled via USB 2.0 / USB 3.x / USB4 / Thunderbolt signaling.
- Video (like connecting to a monitor) is usually handled via DisplayPort Alt Mode or Thunderbolt/USB4.
Manufacturers can (and often do) sell cables that support charging only, because they’re cheaper to make and perfectly fine for a lot of people.
Why a cable might be “charge‑only”
Inside a full‑featured USB‑C cable are extra wires (and shielding) that carry high‑speed data. In a charge‑only cable, those high‑speed data pairs simply aren’t present.
This is common with:
- Cheap bulk cables (the kind you find in a bin at a gas station).
- Promotional/freebie cables.
- Some long cables where the manufacturer cuts cost by omitting data.
- “Fast charging” cables marketed around wattage, not data.
Charging is simple enough that a cable can be functional with fewer conductors. High‑speed data is more demanding: it needs tight manufacturing tolerances and shielding to avoid errors.
“It transfers data… but it’s slow” (USB 2.0 vs USB 3)
There’s a second gotcha: some USB‑C cables do transfer data, but only at USB 2.0 speeds.
USB 2.0 tops out around 480 Mbps (and real-world speeds are often much lower). USB 3.x can be 5 Gbps, 10 Gbps, or 20 Gbps depending on the cable and device. USB4 and Thunderbolt go higher.
Many “charging” cables include just enough wiring for USB 2.0 data (for compatibility), but skip the extra wires for USB 3.x.
Practical consequence: the cable works for syncing a phone, but copying a big video file feels painfully slow.
Fast charging doesn’t imply fast data
It’s completely normal for a cable to support high wattage charging (like 60W or 100W) while still only supporting USB 2.0 data.
That’s because power delivery is mostly about conductor thickness and safety, while high-speed data is about additional data lanes and signal integrity.
What about USB‑C to monitor / dock cables?
If you’re trying to:
- connect a laptop to a USB‑C monitor,
- use a USB‑C dock,
- or run external storage at high speed,
…you usually need a cable that supports USB 3.x (at minimum), and sometimes USB4/Thunderbolt.
Some devices also require that the computer’s USB‑C port supports video output (Alt Mode). A perfect cable can’t fix a port that doesn’t support display output.
How to buy the right USB‑C cable (a simple checklist)
When you’re shopping, look for explicit specs, not vague phrases like “premium” or “fast.”
Decide what you actually need
- Charging only: any reputable USB‑C cable is fine.
- Phone data sync: USB 2.0 is usually acceptable.
- External SSDs / docks: look for USB 3.2 Gen 2 (10 Gbps) or better.
- Monitors / high-end docks: USB4 or Thunderbolt is often safer.
Look for speed in Gbps
- “480 Mbps” or “USB 2.0” = slow data.
- “5 Gbps / 10 Gbps / 20 Gbps” = USB 3.x.
- “40 Gbps” = USB4 / Thunderbolt-class.
Look for power in watts
- “60W” is common.
- “100W / 240W” is for higher-power laptops.
Prefer reputable brands (and returnable listings) USB specs are complicated enough that some cheap listings are simply wrong.
Why your laptop has “USB‑C ports” that behave differently
Even if your cable is perfect, the port matters.
Some computers have a mix of USB‑C ports that support different features. For example, one port might support charging and basic USB data, while another supports video output and high-speed data.
If you’re troubleshooting a dock or monitor, try another USB‑C port before you assume the cable is bad.
Quick troubleshooting: is it the cable, the port, or the device?
If a cable charges but won’t transfer data:
- Try a known-good data cable (like the one that came with an external SSD or a laptop dock).
- Try a different USB‑C port on the computer (some ports are power-only on certain devices).
- If it’s a phone, check the USB mode notification (Android may default to “charging only”).
- Inspect the cable ends: lint or damage can break data even when power still works.
The takeaway: USB‑C is convenient, but the label on the plug tells you almost nothing. When you need data or video, buy based on the printed specs, not the connector shape.