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USB-C Explained: 21st Century’s Super Port

If you’re unsure of the differences between USB-C and Thunderbolt or between USB 3.0 and USB 3.2 (or is that USB 3.1?), you’re not alone.

But mind you, we’ve been in a pretty good place the past few years. Not so long ago, we also had to deal with a myriad of other peripheral connection types, like Parallel, Serial, FireWire, eSATA, etc.

This post will help you understand the current state of modern connection standards — namely USB and Thunderbolt — so that you can confidently plug one device into another.

In getting a peripheral device connected to a host, there are two things to remember: connection type and connection standard. It’s impossible to talk about one without mentioning the other. But let’s start with the connection type.

Dong’s note: I first published this post on  November 13, 2019, and updated it on September 14, 2023, with additional up-to-date information.

Here’s a portable SSD, the Synology BeeDrive, that uses the USB-C connection type.

1. Connection type: How things fit

We generally use a cable to connect a device (like a portable drive) to a host (like a computer). This cable, like all cables, has two ends, which are male connectors or connectors for short.

One end goes into a host, and the other goes into the device. The holes the cable’s ends plug into are female ports or ports for short. The configuration of a port determines its type. Each port type has its corresponding connector.

USB-C port type is the new norm

Most modern devices use USB Type-C (or USB-C for short) port type.

In this case, both ends of the connecting cable are the same: USB-C connectors. It’s super convenient — you don’t need to figure out which end of the wire goes into the host and which is for the device.

The USB-C port also features reversible plug orientation, meaning you can plug the cable in without worrying about keeping a particular side up.

Moreover, the USB-C port type also works as the power connector for large devices, like a laptop — the machine won’t need a dedicated power port anymore — and can deliver power both ways. So, for example, when connecting two smartphones using a USB-C cable, you can share data and power between them.

This convenience is available to the latest USB standards and Thunderbolt 3, which also uses the USB-C port type.

There are subsequent Thunderbolt revisions, including Thunderbolt 4, 5, and even more down the road, but Thunderbolt 3 is the most significant regarding connection type, which is USB-C. For this reason, nowadays, the term “Thunderbolt” is automatically understood as Thunderbolt 3 or later.

In other words, when all of our devices support USB-C, which is the way of the future, there’s no need to worry about what cable to carry anymore since there’s just one type of cable.

Well, almost. For charging, that’s true — virtually any USB-C cable will do, and the charging speed depends on the power source. Unfortunately, things are more complicated regarding data and media purposes. That’s because Thunderbolt and USB are not fully compatible. At least not yet.

Samsung X Portable SSD Thundebolt 3 Cable
The Samsung X5 is a Thunderbolt 3 drive. Note the Thunderbolt 3 cable, which looks identical to a USB-C one.

Port types: Thunderbolt 3 vs USB-C

All Thunderbolt 3 (and subsequent Thunderbolt revisions) ports work as a USB-C-based USB port, but the vice versa is not true. As a result, you can plug a USB portable drive into a Thunderbolt 3 port, and it will work as intended.

However, a Thunderbolt 3-only device, like the Samsung X5 portable drive, will not necessarily work when plugged into a USB-C port, even though its cable fits perfectly. The reason is that Thunderbolt 3 has more requirements than USB 3.2 (and older) standard — more below.

As for the connecting cable, all Thunderbolt 3 cables work as USB-C ones, but only high-quality USB-C cables can also work for Thunderbolt 3 — low-quality ones might work but at a slower speed or are unreliable.

For this reason, a Thunderbolt cable tends to come with the Lightning symbol to distinguish itself from a USB counterpart.

And then we still have to deal with other non-USB-C port types, too.

Legacy USB port types

Synology DS USB Ports
The USB Type-A port is everywhere. Here are two behind this small NAS server.

Since billions of existing USB devices are on the market, it’s essential to support them. As a result, for the foreseeable future, chances are you’ll run into older USB port types.

In this case, the connecting cable has two ends: A and B.

USB Type-A

The end that goes into a host is called a USB Type-A connector.

Before USB-C, this connector and the corresponding port type, the USB-A female port, remained physically the same in all USB standards.

USB Type A 1
USB Type-A and Type-A SuperSpeed connectors. (Not to scale.)

There are two USB Type-A versions (for different USB standards):

  • USB Type-A: Used in USB 1.1 to USB 2.0 and supports speeds up to 480 Mbps.
  • USB Type-A SuperSpeed: Used in USB 3.x standards — more below — and supports speeds up to 10Gbps. It tends to come in blue.

Again, these two types use the same port and work interchangeably (at their respective speeds). In other words, USB Type-A SuperSpeed is backward-compatible with USB Type-A.

If you start getting confused, well, it’ll get much worse.

A Fist Full of USB Cables
Standard USB-Type B variants (clockwise from the bottom): USB-C, Type-B, Mini-B, Micro-B, Type-B SuperSpeed, Micro-B SuperSpeed.

USB Type-B

This type is the other end of the cable that goes into a device and is where things get very complicated.

There are so many variations of standard USB Type-B. That’s not to mention the countless non-standard proprietary Type-B designs, of which the most notorious is the Apple Lighting connector that goes into an iPhone — from iPhone 5 (2012) to iPhone 14 (2022).

Each variant of Type-B connectors requires a corresponding port of its own. Physically, one variant’s connector won’t fit into another’s port. As a result, each port type requires a distinctive cable.

So, for example, if you have an iPhone and another non-Apple device, you’ll have to carry at least two cables.

USB Type B Standards
A few variations of standard USB Type-B connectors. (Not to scale.)

Following are some, out of many, Type-B standards:

  • Standard-B (or Type-B): Used in USB 1.1 and USB 2.0 standards. It suits mostly large devices, like printers or scanners.
  • Standard-B SuperSpeed: Available only to USB 3.x devices, this port type also works best for large devices, like a desktop external drive.
  • Mini-USB (or Mini-B): Significantly smaller than Type-B, this standard is for old portable devices, such as clamshell phones and first-gen portable drives. It’s mostly obsolete now.
  • Micro-USB (or Micro-B): Slightly smaller than Mini-USB, this port was once the go-to type for older smartphones and tablets. It’s also being phased out.
  • Micro-USB SuperSpeed: The thin version of the Standard-B SuperSpeed. It’s popular in portable hard drives, like the WD My Passport.

Again, as you can imagine, with so many port types, finding the correct cable for your device can be a pain in the rear, especially in a hurry. This problem is why the USB-C port type mentioned above is such a knight in shining armor.

All USB-C devices can connect to a USB Type-A port via an adapter or a Type-A to Type-C cable. So going USB-C allows you to get the best of both worlds: the out-of-the-box convenience with modern equipment and the compatibility with legacy devices when need be.

Synology BeeDrive with cable
Here’s the Synology BeeDrive with a USB-C cable with a USB-A to USB-C adapter attached.

Legacy Thunderbolt port type

Even though it is much younger and more “modern” than USB, Thunderbolt once had port issues, too.

That’s because, before Thunderbolt 3, the original Thunderbolt and Thunderbolt 2 used the Mini-Display port type. This standard was one made exclusively for MAC with limited usage.

As a result, there aren’t many “legacy” Thunderbolt devices, and Thunderbolt 3, which is the first revision of the standard available outside of the Apple ecosystem, generally doesn’t support Thunderbolt 2 and Thunderbolt devices. Some can work via an adapter, but they don’t work in most cases.

That said, Thunderbolt 3 is the first revision that breaks away from the Thunderbolt norm to merge with USB in terms of connection type via the USB-C port type.

With that, let’s move on to the connection standard.

2. Connection standard: How (fast) things connect

The connection standard determines how fast a connection is and what you can use it for.

For example, the USB 2.0 standard, determined by the USB Implementers Forum, allows for a connection speed of up to 480 Mbps, and you can also use it to charge a connected device. On the other hand, even the original Thunderbolt can do data, video, and media signals.

We have two primary connection standards, USB and Thunderbolt.

Peripheral connection: Standard vs Type

A connection standard and a connection type are independent concepts.

The type determines if things fit physically, while the standard specifies whether things will work together and how well.

A Thunderbolt 3 device will fit into a USB 3.2 port — both use a USB-C port type. However, it will not work since it requires a different standard.

Here’s an analogy: A car’s gas tank can hold gasoline or diesel — both materials are of the liquid type — but only one will work with the engine, which depends on its combustion standard.

USB standards

Due to multiple name changes of the third USB generation, USB standards can be confusing. Currently, there are the following:

  • USB4: This USB standard was once called USB 4.0. It’s the first USB with built-in display protocols and encompasses Thunderbolt 3. It always uses the USB-C port type. Additionally, it has the best naming convention. USB4 is available in different variants.
    • USB4 20Gbps: 20Gbps a speed cap.
    • USB4 40Gbps: 40Gbps speed cap.
    • Future USB4 v2 variants can deliver up to 80Gbps and more.
  • USB 3.2 with three variants:
    • USB 3.2 Gen 2×2: Formerly USB 3.2, and is another upcoming USB standard despite the availability of USB4. Cap speed: 20Gbps.
    • USB 3.2 Gen 2: Formerly USB 3.1 Gen 2, also called USB 3.1 at one point. This is the mainstream standard. Cap speed: 10Gbps.
    • USB 3.2 Gen 1: Formerly USB 3.1 Gen 1, also widely called USB 3.0. This is the most popular USB standard, with almost all existing devices supporting it. Cap speed: 5Gbps.
  • USB 2.0: This older standard is still quite popular. Cap speed: 480 Mbps.
  • USB 1.1: An ancient standard that’s obsolete. Cap speed: 12 Mbps.

To recap, so far, we’ve had USB 1.1 (obsolete), then USB 2.0 (fading away), then USB 3.2 (mainstream), then USB4 (latest). USB 3.2 Gen 1 (5Gbps) is almost always called USB 3.0. Forget about USB 3.1, and you’ll be less confused.

Now, remember that USB 3.2 doesn’t exist just by itself but in one of three variations, including Gen 1, Gen 2, and Gen 2×2. (Gen = Generation.)

Note that the cap speeds mentioned above are theoretical — real-world sustained USB speeds are generally about two-thirds at best. USB has crazy overheads, and the real-world sustained rates depend on the application. That’s partly because the USB cable has relatively loose requirements.

Via special software or driver, USB 3.2 and older can also deliver sound and video signals but only at certain quality levels, much less than Thunderbolt.

USB can also deliver power to a connected device. For this reason, most, if not all, portable drives don’t require a separate power adapter; they draw juice from the host.

Thunderbolt standards

Relatively young, Thunderbolt has been through four main revisions. Thunderbolt 4 was first announced in July 2020, with devices supporting it being available starting in late 2021.

That said, here is the state of Thunderbolt:

  • Original Thunderbolt: This standard uses the Mini DisplayPort port type and has a cap speed of 10Gbps.
  • Thunderbolt 2: It also uses Mini DisplayPort and has a cap speed of 20Gbps.
  • Thunderbolt 3: Uses USB-C port type. Cap speed: 40 Gbps.
  • Thunderbolt 4: Largely the same as Thunderbolt 3 with some minor improvements. Going forward, newer revisions (TB5, etc.) will also use USB-C port type but with higher bandwidth.

Thunderbolt can do much more than the original USB from the get-go. It can deliver ultra-Hi-Def video/audio signals with high-speed data signals and is a high-wattage power delivery. You can also daisy-chain up to 7 devices together without signal degradation.

Data Transfer Speeds Cable Length Notes
Passive Thunderbolt Cable
(regular wires)
40Gbps (and faster) or 20Gbps Under 2.6ft (0.8m) or over 0.8m plug-n-play
Active Thunderbolt Cable
(with an integrated electronic chip)
40Gbps and faster up to 6.6ft (2m) Draws extra power from the host
Thunderbolt has two types of cable, passive and active. The latter is less common and requires power to work. All USB-C cables work as passive Thunderbolt cables.

You can expect the sustained real-world speeds of Thunderbolt to be near 90% of the specs — it’s much more efficient and reliable than USB. However, again, things depend on the particular application and the cable type/length.

USB vs Thunderbolt

Over the years, these two standards have started to merge by sharing many similarities and overlaps in performance and features.

At launch, a Thunderbolt 3 port also works as USB 3.2 Gen 2 (10Gbps). Slowly, the USB standard can replace Thunderbolt in most cases. However, USB is generally one step behind Thunderbolt in performance and features.

Specifically, USB 4 encompasses Thunderbolt 3, and USB 4 V2 is like Thunderbolt 4, etc. Most importantly, USB still has fewer and less stringent requirements than Thunderbolt. Consequently, it delivers slower sustained speeds and is considered less reliable. But it’s cheaper to implement.

Most general consumers won’t notice the difference between USB and Thunderbolt, but professional users will likely benefit more from the latter.

Thunderbolt 5 vs USB 4 V2 Intel Thunderbolt 5
Intel’s Thunderbolt 5, slated to be commercially available in 2024, will encompass the latest USB 4 standard.

In September 2023, Intel released the specs for Thunderbolt 5, which encompasses the latest USB 4 V2 specifications. The new standards have a ceiling speed of up to 80Gbps, which can be boosted to 120Gbps. You can start to expect to see Thunderbolt 5 devices in 2024.

The table below shows the brief history of these two popular peripheral standards.

Official Name Year Released Port Type
 at Host
Port Type
 at device
Compatibility
(backward)
Ceiling Speed
USB 1.1 1998 Type-A Type-B None 12 Mbps
USB 2.0 2000 Type-A Type-B, USB-C,
proprietary
USB 1.1 480 Mbps
USB 3.2 
Gen 1

(formerly USB 3.0 or 
USB 3.1 Gen 1)
2008 Type-A, USB-C Type-B, USB-C,
proprietary
USB 2.0, USB 1.1 5 Gbps
Thunderbolt  2011 Mini DisplayPort Mini DisplayPort None 10 Gbps
USB 3.2 
Gen 2

(formerly USB 3.1 or 
USB 3.1 Gen 2)
2013 Type-A, USB-C Type-B, USB-C USB 3.2 Gen 1 
USB 2.0, USB 1.1
10 Gbps
Thunderbolt 2 2013 Mini DisplayPort Mini DisplayPort Thunderbolt  20 Gbps
Thunderbolt 3 2015 USB-C USB-C USB-C devices 40 Gbps
USB 3.2 
Gen 2×2

(formerly USB 3.2)
2019 USB-C USB-C USB 3.2 Gen 1/2
USB 2.0, USB 1.1
20 Gbps
USB4
20Gbps
(formerly USB 4.0)
2019 USB-C USB-C Thunderbolt 3
USB-C devices
20 Gbps
USB4
40Gbps
(formerly USB 4.0)
2019 USB-C USB-C Thunderbolt 3 
USB-C devices
40 Gbps
Thunderbolt 4 2020 USB-C USB-C Thunderbolt 3 
USB-C devices
40 Gbps
Thunderbolt 5/USB4 V2 2023 USB-C USB-C Thunderbolt 3
Thunderbolt 4
USB-C devices
80Gbps/120Gbps
Connection standard specifications: USB vs Thunderbolt

The takeaway

With many capabilities, the Thunderbolt’s initial intention is to replace all other wired peripheral connections, including HDMI, DisplayPort, and even USB. But USB has held its ground thanks to its affordability and ease of use.

Slowly, the two peripheral standards have become one in most real-world applications. And that makes sense since they share the same USB-C connection type.

Eventually, from the consumers’ perspective, there will be no difference between these two. And as a result, the USB-C port type is the only thing you need to care about. As for which cable to carry on the go, get passive Thunderbolt (3 or later) for best performance and compatibility, but any with USB-C will do in getting your devices charged.

And that’s a good thing.