Quick answer: USB-C is only the shape of the connector. Speed, video and charging power depend on the standard behind it: plain USB, USB4 or Thunderbolt. Check the spec sheet and the cable rating, because two identical-looking ports can differ a lot.
One cable shape now covers phones, laptops, monitors and drives, which is convenient but confusing. A USB-C port might charge a laptop and drive two displays, or it might only charge a pair of earbuds.
This explainer applies in every region, since the standards are international. It covers what each name means, how fast each is, and how to pick the right cable.
What is USB-C, exactly?
Per Plugable, USB-C is the connector shape, not a speed. The protocols behind it include USB data rates of 5 or 10 Gbps, optional DisplayPort video, and optional USB Power Delivery (PD). Device makers choose which to include, so features vary from device to device.
Macworld puts it the same way in its Thunderbolt and USB4 comparison: plain USB-C ports span a wide range of speeds and functions.
How do USB, USB4 and Thunderbolt compare?
Speeds below come from Plugable and Macworld. They are maximums, and real-world speed depends on the weakest part of the chain.
- USB 3.0 / 3.1 Gen 1: up to 5 Gbps
- USB 3.2 Gen 2: up to 10 Gbps
- USB4: up to 40 Gbps (Macworld says it starts at 20 Gbps); supports one display per Macworld
- Thunderbolt 3: up to 40 Gbps and up to 100 W of power
- Thunderbolt 4: 40 Gbps, with two 4K displays or one 8K display
- Thunderbolt 5: 80 Gbps both ways, up to 120 Gbps for displays with Bandwidth Boost, and up to 240 W of charging power
Thunderbolt 4 is built on the same protocol as USB4, and Thunderbolt 5 works with Thunderbolt 3, Thunderbolt 4 and USB4 devices, according to Macworld. USB4 devices do not need certification, so quality varies more than with certified Thunderbolt gear.
How do I tell what my port supports?
- Look for a lightning-bolt symbol. Plugable says Thunderbolt ports are usually marked with a lightning bolt over a downward-pointing triangle.
- A plain lightning bolt on USB-C may mean power delivery, and a “DP” logo means DisplayPort video.
- Many ports are unmarked. Check the maker’s spec sheet for port type, count and speed.
- On Macs, Macworld says base M1 and M2 models and iPad Pro show “Thunderbolt / USB 4” because they cannot drive multiple displays.
If you are comparing laptops, our guide to whether to buy a laptop now or wait covers the market, and ports are worth checking before you buy.
How do I choose the right cable?
A fast port is wasted on a slow cable. Macworld notes in its guide to USB-C logos that the USB Implementers Forum introduced logos for certified cables. A USB4 cable shows “40Gbps”, and a USB PD 3.1 cable shows either 60W or 240W. Gigazine adds that these logos appeared in October 2021, with seven designs in total.
Cable checklist
- For laptop charging above your charger’s basic rating, buy a cable rated for that wattage. Macworld says a 240W-rated cable is required for 240W charging.
- For fast drives and docks, look for the 40Gbps logo or Thunderbolt branding.
- Length matters. Macworld says passive Thunderbolt 5 cables reach 1.2 m before needing costlier active parts, and Thunderbolt 4 passive cables are limited to about 0.8 to 1 m.
- Logos are voluntary. Macworld stresses they confirm design requirements only, not durability, and a cable without logos could still perform well.
Does it matter for storage?
Yes. A fast external SSD on a 5 Gbps port or a slow cable runs well below its rating. With drive prices high, see our note on backup options as drive prices rise. More explainers are in more tech news.
Which should you buy: USB4 or Thunderbolt?
For most people, a USB4 or Thunderbolt 4 port is plenty. It handles fast drives, a dock and one or two monitors. Thunderbolt 5 matters mainly for high-end setups, such as several high-resolution displays or very fast storage, where its 80 Gbps shows.
Because Thunderbolt 4 and 5 products are certified, they are a safer buy when a dock or monitor must work reliably. USB4 is fine for simpler jobs, but check the spec sheet for display and charging support, since Macworld notes USB4 ports support only one display. Everything is backward compatible, so an older device still works, just more slowly.
Power is the other thing to check. Plugable explains that PD lets a charger and device negotiate voltage and current, for example a phone at 9V and 3A or a notebook at 20V and 5A. If a laptop charges slowly, the cable or charger may be the limit, not the port.
Frequently asked questions
Is USB-C the same as Thunderbolt?
No. They share the connector. Thunderbolt adds higher speeds and more features, and Plugable says USB-C devices work on Thunderbolt ports without the full Thunderbolt features.
Can I use a Thunderbolt device on a normal USB-C port?
Usually yes, at reduced speed or with fewer display outputs, per Plugable.
What is the difference between USB4 and Thunderbolt 4?
Thunderbolt 4 is Intel’s USB4 implementation with optional features enabled, according to Plugable. It also requires certification.
Do I need a 240W cable?
Only for devices that charge at that rate. For phones, any properly rated cable is enough.