Here’s what I tell people about the difference between USB 4 and USB-C

I probably don’t have to tell you that the situation with USB ports has become a little complicated, no matter that the U is supposed to stand for “universal.” While you’re not going to find USB 1.0 hardware lingering around, there are still many different speeds, and using the wrong port or cable can severely bottleneck performance — the jump between 2.0 and 3.0 is night-and-day if you’re trying to backup your computer. On top of that there are multiple connector types in circulation, which can quickly get confusing if you’ve got a bunch of older accessories sitting in boxes. When my wife and I moved last year, I spent a surprising amount of time figuring out which cables I should get rid of.

If you’re shopping for a new phone, tablet, laptop, or other device, two terms you’re going to see bandied around a lot are USB 4 and USB-C. It’s important to know the distinction between the two, although they often go hand-in-hand. You should almost always insist on USB-C, but not necessarily USB 4. I’ll try to explain the reasons as best I can.

What is USB-C, and why does it matter?

A solution to several problems

USB-C is a port/connector type that debuted in 2014. It was meant to solve a few problems with earlier incarnations of USB, perhaps the most infamous being reversibility. Simply put, earlier formats like micro-USB and USB-A — the second being the bigger, rectangular one you’ll still find on many devices — were non-reversible. There was a distinct “up” side to a port, so it was all too common for people to fumble around trying to connect a cable. A long-standing truism in tech circles was that you could never insert a USB-A cable correctly on the first try, and it certainly felt that way.

Aside from being reversible, USB-C is also compact. That means it can fit on just about any device without speed or power compromises. Every smartphone now uses USB-C, even iPhones, in spite of Apple’s long refusal to abandon its proprietary Lightning standard. You can also find USB-C on products like smartwatches, action cameras, and other gadgets that would’ve previously depended on micro-USB or some custom technology. In the European Union, USB-C is actually a mandatory standard for wired charging on many devices. That’s how Apple was finally forced to give up the ghost.

Speaking of power, that’s another key feature. While USB has long supported charging devices like phones and mice, ports and cables supporting USB-C Power Delivery (USB PD) can deliver considerably more juice. Often that’s up to 100W, enough to power many laptops. Products compatible with USB PD Revision 3.1 can supply up to 140, 180, or even 240W — for a frame of reference, my last gaming laptop shipped with a gigantic 240W power brick. The tech is so effective that USB-C is frequently used in place of conventional power cables, as on my Eero Wi-Fi routers. You do need to check that your device, cable, and wall adapter all support the flow you’re expecting.

What USB-C doesn’t specify is data rates. Some devices, like the iPhone 16, operate at USB 2.0’s 480Mbps limit. That might sound like a lot when weighed next to your internet connection, but the 2.0 spec is a quarter-century old, and can be painfully slow for local file transfers. Copying 1GB at 2.0 speeds takes about 30 to 50 seconds — backing up a 1TB hard drive might take anywhere between eight and 14 hours. There’s a reason many people only ran backups overnight in the 2000s.

More commonly, USB-C ports are equipped for at least USB 3.1 Gen 1, which runs at 5Gbps. It’s a dramatic speed boost, capable of handling that 1TB backup in less than 40 minutes. You’ll get identical speeds out of USB 3.2 Gen 1×1. Performance doubles to 10Gbps with USB 3.1 Gen 2/USB 3.2 Gen 1×2, and quadruples to 20Gbps with USB 3.2 Gen 2×2. In practice, you probably won’t see Gen 2×2 very often. It wasn’t adopted that widely before USB 4 came along.

What’s the big deal with USB 4?

Not just a speed boost

USB 4 — note the absence of a decimal point — is primarily a speed standard. All USB 4 products support at least 20Gbps. The majority can handle 40Gbps, which is almost unbelievable next to what existed five years ago, never mind a decade or two. It’s so fast that in many cases, the only limitation is going to be your storage, not the way you’re transferring data. Many SSDs can’t max out a USB 4 pipeline.

In 2022, the USB Promoter Group released an updated specification dubbed USB 4 Version 2.0, usually shortened to USB 4 v2. This supports up to 80Gbps symmetrically, or 120Gbps unidirectionally, with the other path being reduced to 40Gbps. Be aware that many tablets and computers are still limited to v1, and v2 accessories are only now starting to proliferate, often with a high price premium attached. Double-check which version you’re getting before buying anything. When in doubt, assume you’re getting v1 speeds.

Critically, USB 4 v1 offers Thunderbolt 4 compatibility, while v2 supports Thunderbolt 5. Think of Thunderbolt as a stricter implementation of USB that ensures maximum performance — Thunderbolt accessories are often the gold standard for professionals, such as video editors and music producers. Even if you aren’t a pro, however, there are numerous Thunderbolt docks and SSDs on the market. A dock can be immensely useful for setting up a laptop workstation — I use my own to connect a mouse, keyboard, Ethernet cable, and headphones while only taking up one of my PC’s ports. If I want to take my laptop somewhere, all I have to do is unplug its power and Thunderbolt cables. I could hook up a 4K monitor too, if I had one.

Thunderbolt 5 is capable of handling two 4K monitors at 120Hz, and supplying as much as 240W of downstream power. It’s also quick enough to support some modern video cards via an eGPU enclosure, which can provide a major boost to graphics performance if your PC doesn’t have a dedicated GPU of its own. Don’t expect too much from this, mind you. There’s no point in installing a high-end card like Nvidia’s GeForce RTX 5080, and the enclosure itself will cost a few hundred dollars before you’ve found anything to put in it. You may be better off saving the money for a purpose-built gaming PC.

All USB 4/Thunderbolt cables use a USB-C connector. This stands in contrast with USB 2.0 and 3.x, which sometimes operate over USB-A. In a few years this shift should bury USB-A for good. Don’t worry if you’ve still got an array of USB-A devices, though, since adapter cables should ease the transition. You just won’t be able to achieve USB 4 speeds until your devices have the ports to match. Even that may not be a big deal unless you’re working with 4K video files, or simply can’t stand the idea of a backup taking more than a few minutes.