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.
Mind you, we’ve been in a pretty good place in the past half a decade. Before that, we 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.
Tip
The year 2023 was the most significant for peripheral connectivities.
After years of pressure from the EU, Apple finally had to give up its greed and forgo the proprietary Lightning connector. The iPhone 15 was the first in the family, and the final major electronic device in the world, to adopt USB-C as its charging port.
Additionally, the latest USB 4 V2 standard was released in June, and Intel also announced Thunderbolt 5 in September.
When connecting a peripheral device 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 former: the connection type.
Dong’s note: I first published this post on November 13, 2019, and updated it on March 9, 2025, with additional up-to-date information, including tips on USB Power Delivery.
1. Connection type: How things fit—it’s connector vs. port
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, or you can say each connector type has a corresponding port. Either is correct.
USB-C port type is the new norm
Most modern devices use the USB Type-C port type (or USB-C for short).
In this case, both ends of the connecting cable are the same: they are USB-C connectors. This is 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 a power connector for devices, like a laptop or a phone—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. (We’ll learn more about USB power delivery below.)
This port-type convenience is available to the latest USB standards and Thunderbolt 3, which also uses the USB-C port.
Tip
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 has been the mandate since the EU forced Apple to part ways with its Lighting connection type, 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—more on this below.
Unfortunately, things are more complicated regarding data purposes. That’s because Thunderbolt and USB are not two fully compatible connection standards.
Connection types: Thunderbolt 3 vs. USB-C
All Thunderbolt 3 (and subsequent Thunderbolt revisions) ports work as a USB-C-based USB port, but not vice versa.
As a result, you can plug a USB portable drive into a Thunderbolt 3 port, and it will work as intended. However, a Thunderbolt-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 in terms of connection standard than USB 3.2 (and older), which we’ll discuss 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 have the Lightning symbol to distinguish itself from a USB counterpart.
And then, chances are we’ll still have to deal with other non-USB-C port types for years to come.
Connection types: Legacy USB
Since there are billions of existing USB devices on the market, modern host devices need to support them. As a result, chances are you’ll run into older USB port types for the foreseeable future.
In this case, our beloved connecting cable has two different ends: A and B.
USB Type-A (the host end)
The end of a connecting cable that goes into a host, such as a computer, 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.
There are two USB Type-A versions (for different USB standards—more below):
- 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, though 5Gbps is more common. 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 to get confused, well, it’ll get much worse.
USB Type-B (the device end)
This type is the other end of the cable that goes into a device, such as mp3 players or legacy smartphones, 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. Physically, one variant’s connector won’t fit into another’s port, so 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.
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 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 of modern equipment and the compatibility with legacy devices when needed.
Connection types: Legacy Thunderbolt
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, made exclusively for Apple, used the Mini-Display port type. And Apple, with its usual greed and desire to control, intended to keep things that way, rendering Thunderbolt up to then borderline useless.
As a result, there aren’t many “legacy” Thunderbolt devices.
Recognizing how Thunderbolt would eventually be killed off if it stayed exclusively with Apple, in late 2015, Intel made Thunderbolt 3 as a public revision. It does not support the original Thunderbolt and Thunderbolt 2 devices. Some can work via an adapter, but most don’t.
In short, Thunderbolt 3 is the first revision that breaks away from Apple’s handcuffs to merge with USB in terms of connection type via the USB-C port type. In many ways, it’s the first actual Thunderbolt revision since it’s the first also available to Windows and other platforms.
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.
Tip
If the host and the device don’t share the same connection standard, there are no data or power activities between them despite the wire that physically connects them.
For example, the USB 2.0 standard, determined by the USB Implementers Forum, allows for a data connection speed of up to 480 Mbps, and you can also use it to charge a connected device per a specific power charging standard. On the other hand, Thunderbolt can deliver data, video, media signals, and power simultaneously.
We have two primary connection standards, USB and Thunderbolt, each with its versions (or variants, revisions, or sub-standards).
Peripheral connection: Standard vs. Type
A connection standard and a connection type are independent concepts.
The type determines whether things fit physically, while the standard specifies how, and how well they will work together.
A Thunderbolt 3 storage 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 data standard.
Here’s an analogy: A car’s gas tank can hold gasoline or diesel—both are the liquid type of materials—but only one will work with the engine, which depends on its combustion standard.
Connection standard: USB variants
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 speed cap.
- USB4 40Gbps: 40Gbps speed cap.
- USB4 v2 can deliver up to 80Gbps and even more.
- USB 3.2 with three variants:
- USB 3.2 Gen 2×2: Formerly USB 3.2, and is another “fast” 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), USB 2.0 (fading away), USB 3.2 (mainstream), and USB4 (latest).
Now, remember that USB 3.2 doesn’t exist alone but in one of three variations, including Gen 1, Gen 2, and Gen 2×2. The easiest way to deal with USB 3.2 is to call it by its speed caps: we have USB 5Gbps, USB 10Gbps, and USB 20Gbps.
Note that the cap speeds mentioned above are theoretical—real-world sustained USB speeds are generally about two-thirds at best. Due to forgiving implementation requirements, USB has crazy overheads.
In addition to data, USB 3.2 and older can also deliver sound and video signals, but only at certain quality levels, much less than Thunderbolt.
Another significant application of USB is that it can deliver power to a connected device. As a result, portable drives generally don’t require a separate power adapter—they draw juice from the host.
Connection standard: Thunderbolt variants
Relatively young, Thunderbolt has been through five or three main revisions depending on who you ask, including:
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: This is the first true Thunderbolt standard. It uses a USB-C port type. The cap speed is 40 Gbps.
- Thunderbolt 4 and 5: These are essentially the same as Thunderbolt 3, with incremental improvements and bandwidth. They both use the USB-C port type.
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 slower) or 20Gbps | Up to 2.6ft (0.8m) or longer | 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’s sustained real-world speeds are 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.
Connection standards: 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 and 4 port also works as USB 3.2 Gen 2 (10Gbps). Thunderbolt 5 features USB 3.2 Gen 2×2 and USB4 (20Gbps). Slowly, the USB standard can replace Thunderbolt in some instances.
However, USB is generally one step behind Thunderbolt in terms of performance and features. Specifically, USB 4 encompasses Thunderbolt 3, and USB 4 V2 is like Thunderbolt 4, etc.
As mentioned, USB has fewer and less stringent requirements than Thunderbolt. Consequently, it has more overhead, delivers slower sustained speeds, and is considered less reliable. But it’s cheaper to implement.
General consumers will not notice the difference in performance between USB and Thunderbolt, but professional users will likely benefit more from the latter.
In September 2023, Intel released 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. The first devices with Thunderbolt 5 became available 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 |
More than just data: USB Power Delivery standards
Power delivery in the USB port is a bit less confusing than data connections. This is not because the technology is simple but because it’s made so that consumers won’t need to remember much—all they need to do is plug the device in.
However, if you want to know more, keep the tip below in mind.
Tip
Electricity is somewhat like water. There are three things involved:
- Voltage (V) or Potential Difference: The volume of electricity or the size of the potential force to be sent over the wire. It’s like the amount of water with its built-up pressure before you open the valve.
- Ampere (A) or Current: The size of the energy flow. It’s the pipe size in the flow of water. (Miliampere-hour or mAh is the unit for small batteries’ capacities)
- Watts (W) or Power: The amount of energy being delivered or consumed in real time. In water delivery, it’s the flow of the liquid from one container to another. Watts over a period of time—measured in Watt hour (Wh) or Kilowatt-hour (kWh)—indicate the amount of energy consumed, delivered, or accumulated and are used to show the capacity of large batteries, such as those in EVs.
Here’s the relationship between these three:
V * A = W
The higher the wattage, the faster electricity can move from one place to another (charging speed) or the more energy it can produce (power output).
Now, there are a few other things to note about USB power delivery:
First, prior to USB-C, the max power a USB-A port could deliver was 15W (or 5V * 3A) regardless of the USB standard. This is still true today. If you see a USB-A port, chances are it can’t deliver more than 15W in charging. In modern USB chargers or power banks, the USB-A will deliver up to 15W and support all previous charging speeds available to the port.
Secondly, with USB-C, since 2012, we’ve had the USB Power Delivery (PD) standards with lots of charging profiles, ranging from 10W to 240W of charging speed, though the 100W max is more common and is already more than enough for most large devices. A laptop generally needs a 45W to 65W power adapter.
The tables below show the current USB Power Delivery standards. Again, the higher the wattage, the faster the charging speed (or higher the power output).
| Charging Profile | Voltage | Ampere (current) |
Wattage (charging speed) |
Applicable Devices |
|---|---|---|---|---|
| 1 | 5V | 2A | 10W | portable SSDs, smartphones, small accessories |
| 2 | 12V | 1.5A | 18W | Large accessories, smartphones, tablets, ultra-compact laptops |
| 3 | 12V | 3A | 36W | Laptops, display, hub, powerbanks |
| 4 | 20V | 3A | 60W | Large laptops, docking stations |
| 5 | 20V | 5A | 100W(*) | Laptops, display, hub, power banks |
| Charging Profile | Voltage | Ampere (current) |
Wattage (charging speed) |
Applicable Devices |
|---|---|---|---|---|
| 1 | 5V | .1A to 3A | 10W | Headphones, earbuds, small accessories |
| 2 | 9V | 1.67A to 3A | 15W to 27W | Smarthones, cameras, drones, toys |
| 3 | 15V | 1.8A to 3A | 27W to 45W | Tablet, small laptops |
| 4 | 20V | 3A to 5A | 45W to 100(*) | Large laptops, displays, hubs |
| 5 (added via USB PD 3.1)(**) |
28V, 36V, 48V | 5A | 140W, 180W, 240W | Desktops, large appliances |
(**)High-power USB Type-C cable required.
Finally, no matter what USB PD standards, the following are generally true:
- A higher-charging-profile power source does everything lower ones do.
- A higher-charging-profile device can draw power from lower-charging-profile power sources.
- For safety reasons, USB Power Delivery maxes at 5A. For 45W or lower, generally any USB-C cable will work, but for higher output wattage, it’s best to use a cable rated for that wattage.
The point is that, in terms of charging, you can plug any USB-C-enabled battery-powered device into any USB-C power source without worrying about “frying” it. The power source will automatically deliver its max charging speed or the max charging speed supported by the device, whichever is lower.
However, if your device uses a USB-C power port but doesn’t have a battery, such as a router or a printer, it will need to be plugged into a charger of the same or higher charging profiles to work.
That said, when it comes to buying a charger or power bank, it’s best to get one with the highest power output (in watt) within the physical size you want. Additionally, it’s best to use high-quality cables rated for 100W or higher, though if you have small (low-wattage) devices, any USB-C cable will do.
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.
Most importantly, from the consumers’ perspective, there’s no difference between these two when it comes to getting their devices charged. And that’s a good thing.
