USB-C was supposed to be the one cable to rule them all. One connector for charging, data transfer, video output, and everything else. And physically, that’s true — the connector is the same everywhere. But the capabilities of the cable behind that identical connector vary enormously, and the labelling is a mess.

That $5 USB-C cable from the petrol station might charge your phone slowly, refuse to output video, transfer data at USB 2.0 speeds (from 2000), or in the worst case damage a device by not handling power delivery correctly. Here’s why, and how to avoid the pitfalls.

The Problem: One Connector, Many Standards

A USB-C connector can support any of the following protocols, in various combinations:

• USB 2.0 — 480 Mbps data transfer
• USB 3.2 Gen 1 — 5 Gbps (formerly USB 3.0)
• USB 3.2 Gen 2 — 10 Gbps (formerly USB 3.1)
• USB 3.2 Gen 2x2 — 20 Gbps
• USB4 — 40 Gbps
• Thunderbolt 3/4 — 40 Gbps with additional features
• DisplayPort Alt Mode — video output
• HDMI Alt Mode — video output
• USB Power Delivery — up to 240W charging (with the EPR extension)

A cable might support some of these and not others. The connector looks identical regardless. There’s no way to tell from looking at a cable what it supports.

This is a genuine design failure in the USB-C ecosystem. The USB Implementers Forum has been trying to fix it with labelling standards, but adoption is inconsistent and the labelling itself is confusing.

Charging Differences

Not all USB-C cables carry the same power. The differences are significant:

Basic USB-C cables support 5V/3A — that’s 15W. Fine for slowly charging a phone, not great for a laptop.

USB PD (Power Delivery) cables support negotiated voltages up to 20V at 5A (100W) or, with the newer EPR spec, up to 48V at 5A (240W). Your laptop charger’s 65W-100W output requires a cable that supports these higher power levels.

The resistance problem. Cheap cables use thinner conductors with higher electrical resistance. Higher resistance means more energy lost as heat and less power reaching your device. A cable rated for 60W might technically charge a 45W laptop, but it’ll run hot and charge slowly. Some poorly made cables have caused overheating incidents.

E-marker chips. Cables rated for more than 60W are required to contain an electronic marker (e-marker) chip that communicates the cable’s capabilities to the devices at each end. Cables without e-markers are limited to 60W regardless of what the packaging claims. Many cheap cables skip the e-marker to save costs.

If you’re charging a laptop or high-powered device, make sure the cable explicitly supports USB PD at the wattage you need. The cable that came with your phone charger probably doesn’t.

Data Transfer Differences

This is where it gets really confusing. A USB-C cable with a USB 2.0 connection inside only transfers data at 480 Mbps — about 60 MB/s. A cable with USB 3.2 Gen 2 reaches 10 Gbps — about 1.2 GB/s. That’s a 20x difference, and both cables look identical.

Why do USB 2.0 cables with USB-C connectors even exist? Because they’re cheaper to manufacture. They use fewer wires internally (4 vs 24 for a full-featured cable) and don’t need the signal integrity engineering required for high-speed data.

Most cables bundled with phones are USB 2.0. They’re fine for charging and basic data transfer. But if you’re connecting an external SSD, docking station, or display, you need a cable that supports the appropriate data standard.

How to tell: Look for explicit speed ratings on the packaging. “USB 3.2 Gen 2” or “10Gbps” means high-speed data. If the packaging just says “USB-C cable” without a speed rating, assume USB 2.0.

Video Output Differences

USB-C can carry DisplayPort video signals through Alt Mode. But only cables with the right internal wiring support this. A USB 2.0 cable with a USB-C connector physically cannot carry a DisplayPort signal — it doesn’t have the necessary conductors.

If you’re connecting a laptop to an external monitor via USB-C, you need a cable that supports either:

• DisplayPort Alt Mode (most common)
• Thunderbolt 3/4 (which includes DisplayPort)
• USB4 (which includes DisplayPort)

Again, the packaging should specify. If it doesn’t mention video, display, Thunderbolt, or USB4, it probably doesn’t support video output.

Cable Length and Signal Integrity

Longer cables degrade signal quality. For high-speed data (USB 3.2 and above), passive cables should ideally be under 2 metres. At 3 metres, some passive cables start experiencing errors or falling back to lower speeds.

For USB4 and Thunderbolt at 40 Gbps, maximum passive cable length is effectively 0.8-1 metre. Longer runs require active cables with signal boosting electronics built in. Active cables are significantly more expensive.

For charging, longer cables increase resistance and reduce delivered power. A 3-metre cable will charge your device more slowly than a 1-metre cable, all else being equal.

The Labelling Mess

The USB Implementers Forum has attempted to standardise labelling with logos and certification programs. As of 2026, the official labelling uses speed ratings:

• USB logo with “5” = USB 3.2 Gen 1 (5 Gbps)
• USB logo with “10” = USB 3.2 Gen 2 (10 Gbps)
• USB logo with “20” = USB 3.2 Gen 2x2 (20 Gbps)
• USB logo with “40” = USB4 (40 Gbps)

Power delivery capability is indicated separately with a wattage rating (60W, 100W, 240W).

This is clearer than the previous naming chaos, but many cables on the market — especially cheaper ones — don’t carry these logos or carry misleading labelling. Amazon and eBay are full of cables claiming speeds they don’t actually support. The USB-IF certified cable list can verify legitimate certifications, but most consumers won’t check.

Practical Buying Advice

For phone charging: Almost any USB-C cable works. Get one that supports your charger’s wattage (check the charger’s output spec) and don’t stress about data speed unless you’re transferring files.

For laptop charging: Get a cable explicitly rated for USB PD at your charger’s wattage (usually 65W or 100W). Cables from reputable brands (Anker, Apple, Belkin, Cable Matters) are reliable. Avoid unbranded cables for laptop charging.

For external storage: You need a cable rated for at least USB 3.2 Gen 1 (5 Gbps). For NVMe SSDs, get USB 3.2 Gen 2 (10 Gbps) or higher. Keep the cable as short as practically possible.

For displays: Get a cable explicitly supporting DisplayPort Alt Mode, Thunderbolt, or USB4. For 4K displays at 60Hz, Thunderbolt or USB4 is recommended.

For docking stations: Thunderbolt or USB4 cables. These support data, video, and power simultaneously. Expect to pay $20-$50 AUD for a quality cable.

General rule: Buy cables from reputable brands with clear specifications on the packaging. The price difference between a reliable cable and a questionable one is typically $10-$20 — trivial compared to the cost of the devices you’re connecting.

USB-C is a great connector. The standards behind it are a confusing mess. Until labelling improves and the market clears out non-compliant cables, the burden falls on consumers to understand what they’re buying. It shouldn’t be this complicated, but it is.