Every USB-C cable fits every USB-C port — and that’s exactly the problem. Two identical-looking cables can differ by a factor of 80 in data speed, one may carry video and the other not, and one may charge your laptop at full speed while the other trickles. This guide explains what actually varies, how to tell cables apart, and which ones to own.
The short version
- Most USB-C cables in a drawer are USB 2.0: fine for charging, slow for data (480 Mbps), no video.
- Power: 60W needs nothing special; 100W and 240W need cables rated for it (they contain an e-marker chip).
- Video requires a cable that supports DisplayPort Alt Mode or Thunderbolt.
- One cable to own: a certified Thunderbolt 4 / USB4 cable — 40 Gbps, video, and 100W charging in one.
Three things vary independently
1. Data speed
| Standard | Speed | Typical use |
|---|---|---|
| USB 2.0 | 480 Mbps | Charging cables, phone sync — most bundled cables |
| USB 3.2 Gen 1 | 5 Gbps | Basic external drives, hubs |
| USB 3.2 Gen 2 | 10 Gbps | Fast external SSDs |
| USB 3.2 Gen 2×2 | 20 Gbps | High-speed SSDs on Windows PCs |
| USB4 / Thunderbolt 3, 4 | 40 Gbps | Docks, multiple displays, NVMe enclosures |
| Thunderbolt 5 | 80 Gbps and above | Newest Macs and high-end PCs |
A USB 2.0 cable will happily charge a laptop, but copying files through it — or plugging a dock into it — will be painfully slow. See best external SSDs for what these speeds mean in practice.
2. Power
| Rating | Requirement | Charges |
|---|---|---|
| Up to 60W (20V/3A) | Any standard USB-C cable | Phones, tablets, thin laptops |
| Up to 100W (20V/5A) | Cable with an e-marker chip, rated 5A | Most laptops |
| Up to 240W (EPR) | USB PD 3.1 / EPR-rated cable | Large and gaming laptops |
Using an underrated cable isn’t dangerous — the devices negotiate down — but you’ll get slow charging and wonder why. More in our USB-C charger guide and power bank guide.
3. Video
To drive a monitor, the cable must support DisplayPort Alt Mode or be a Thunderbolt/USB4 cable — and the laptop port must support video output too. This is the most common reason a “USB-C monitor” shows nothing when connected with a random cable.
How to tell cables apart
- Look for logos near the connector: a lightning-bolt Thunderbolt icon (often with a 3, 4 or 5), an SS (SuperSpeed) mark with 10 or 20, or a wattage number like 240W.
- Length is a hint: passive 40 Gbps cables are short, typically up to about 0.8m. A 2m cable claiming 40 Gbps must be an active (and pricier) cable.
- Buy certified: USB-IF certified or Thunderbolt-certified cables from known brands (Apple, Anker, Belkin, CalDigit, UGREEN, Cable Matters).
- Label your cables with tape or colored ties once you know what they are — future you will be grateful.
- Test a suspect cable by copying a large file to an SSD and watching the transfer speed.
What to own
| Cable | Why |
|---|---|
| One Thunderbolt 4 / USB4 cable (0.8m) | Docks, monitors, fast drives — does everything |
| One or two 100W charging cables (1.8–2m) | Charging at the desk and beside the bed |
| One 240W cable | Only if you have a high-wattage laptop or power bank |
| A short 10 Gbps cable | For a portable SSD in the bag |
Troubleshooting checklist
- Monitor not detected: wrong cable (no video support) or a laptop port without DisplayPort Alt Mode.
- Laptop charging slowly: cable rated below the charger’s output, or a charger sharing power across ports.
- External SSD slow: USB 2.0 cable, or plugged into a USB 2.0 port.
- Dock flaky: use the cable that came with the dock; cheap long cables are the usual culprit.