Making Sense of USB-C and Thunderbolt Cables and Ports on Your MacBook
The latest MacBook Pro sheds almost all ports; it includes only a headphone jack, a few USB-C connectors, and it also supports the latest high-speed Thunderbolt 3 standards. What’s the difference?
Despite the “U” in USB standing for “universal,” the standard has come under fire for confusing consumers. Some cable manufacturers have been accused of breaking standards, and cheap USB-C cables might even damage your electronics.
Let’s try and make sense of this mess of MacBook ports.
What Is USB-C?
Also known as USB Type-C, USB-C is a symmetrical connector designed to replace the existing Type-A and Type-B connectors. Unlike its predecessors, you can insert USB-C any way. That means no more fishing around in the dark wondering whether you’re holding the cable the right way round.
USB-C strictly relates to the shape of the connector and the port into which it fits. It’s not a standard for data transmission, like USB 2.0 or 3.1. Despite USB-C using a 24-pin connector, many different standards have used the USB-C shape.
All USB-C cables must be able to carry at least a 3A current up to 60W at 20V. Many smartphones use the USB-C standard to facilitate fast charging, which pulls in a higher voltage thanks to the increased power throughput.
Some USB-C cables can carry 5A for 100W at 20V, enough to charge the latest high-end MacBooks and HP Spectre line of laptops (to name but a few). Devices using the USB-C standard for data and power transfer include Google’s Pixel smartphones, the latest MacBook Pro, the Nintendo Switch, and many portable USB batteries.
USB-C’s Alternate Modes
Not all USB-C cables are made equal. Many devices, like the latest MacBooks, let you use USB-C cables for a range of “Alternate Modes” including:
- DisplayPort Alternate Mode: Send DisplayPort video using the new-shape USB-C connector.
- Mobile High-Definition Link (MHL) Alternate Mode: Send MHL audio and video using USB-C.
- Thunderbolt Alternate Mode: Connect Thunderbolt devices using the USB-C connector.
- HDMI Alternate Mode: Send HDMI audio and video via USB-C.
There’s something important to note if you intend on using any of these standards. You must buy a cable that explicitly states it is compatible with the mode you want to use. So if you want to connect your TV to your MacBook over USB-C, make sure the cable supports HDMI Alternate Mode.
What Is Thunderbolt 3?
Thunderbolt is a hardware interface developed by Intel and Apple, introduced to the market in 2011. Thunderbolt 3 is the latest iteration of this standard, which has become a signature MacBook port. Whereas the first two generations of Thunderbolt devices used the Mini DisplayPort connector, Thunderbolt 3 uses USB-C exclusively.
Much of the confusion surrounding USB-C and Thunderbolt relates to the shape of the connector. You cannot buy Thunderbolt 3 cables that don’t use the USB-C standard. At the same time, Thunderbolt 2 cables don’t fit into Thunderbolt 3 ports since they’re a different shape (they are backwards-compatible with the right adapter though).
Thunderbolt 3 improves on the standard in almost every way. It doubles the bandwidth of the previous generation to 40Gbps. It’s now also USB compatible, which means it can combine multiple technologies into one port. Add to this the array of Alternate Mode applications as outlined above, and you’ve got one port to rule them all.
The latest standard supports HDMI 2.0, DisplayPort 1.2 (with resolutions up to 4K), and PCIe 3.0. This provides enough bandwidth to finally realize the potential of external graphics cards. It can also incorporate USB Power Delivery, with up to 100w of power throughput. This is how Apple was able to replace MagSafe power connectors with USB-C ports on its latest machines.
Thunderbolt has one last trick up its sleeve: daisy chaining. You can connect Thunderbolt devices in a daisy chain, allowing you to link multiple devices together and still only use a single USB port on your computer.
The superior speeds and connectivity over USB 3.1 and similar standards are made possible because Thunderbolt cables are active. A microchip built into the connector enables higher performance and greater versatility than standard “passive” USB cables. You can still use passive USB-C cables used to connect some Thunderbolt 3 devices, but they will work at much slower speeds.
Compatibility With MacBook and Other Macs
The following Apple computers are compatible with Thunderbolt 3, using USB-C connectors:
- MacBook Pro, late 2016 and newer
- iMac, mid 2017 and newer
- iMac with Retina Display, mid 2017 and newer
- iMac Pro, late 2017 and newer
The following Apple computers are compatible with Thunderbolt 2, using Mini DisplayPort connectors:
- MacBook Pro Retina, late 2013-mid 2015
- MacBook Air, early 2015-mid 2017
- iMac, late 2015
- iMac with Retina Display, late 2014-late 2015
- Mac mini, late 2014
The following Apple computers are compatible with the original Thunderbolt standard, using Mini DisplayPort connectors:
- MacBook Pro Retina, mid 2012-early 2013
- MacBook Air, mid 2011-early 2014
- iMac, late 2012-mid 2014
- Mac mini, mid 2011-late 2012
Not sure which computer you have? Boot it up, log in, and click on the Apple menu in the top-left of the screen. Select About This Mac and you’ll see information pertaining to your model beneath your current macOS version number. Note that the regular MacBook model doesn’t support Thunderbolt at all, just USB-C and USB 3.1.
Thunderbolt 3 Cables and Adapters
Apple does not supply a Thunderbolt 3 cable with new MacBooks. The USB-C cables and adapters used to charge Apple’s latest laptops are only capable of USB 2.0 speeds. Depending on the model, these can carry power throughputs of 27W, 60W, and 87W at maximum load.
Buying the right cable is important. If you’re buying a cable to use with your new USB-C Mac, you have two choices: USB or Thunderbolt.
In terms of speed:
- USB 3.1 gen 1 (also known as SuperSpeed USB 3.0) supports up to 5Gbps
- USB 3.1 gen 2 supports up to 10Gbps
- Thunderbolt 1 up to 10Gbps
- Thunderbolt 2 up to 20Gbps
- Thunderbolt 3 up to 40Gbps
USB-C cables come in a variety of speeds and configurations. The thicker (5A) cables will carry a higher voltage and allow you to charge more power-hungry devices. USB is fully backwards compatible, and you can even use USB-C with the traditional USB-A connector if you buy an adapter.
USB-C cables will have some limited Thunderbolt compatibility, and transfer speeds may even exceed those of USB 3.1. However, because USB-C cables are passive and not active, they are no replacement for Thunderbolt 3 cables. Check out our roundup of the best USB-C cables.
Thunderbolt 3 cables are generally more expensive, since they have more technology inside them. They aren’t always compatible with the USB 3.1 gen 2 standard, especially if they’re longer than around 1.5 feet.
Thunderbolt 3 or Not: What’s Best for My Needs?
If you’re confused, you’re not alone. The industry has done little to ease the head-scratching that comes with deciphering which peripheral you need. If in doubt, look at what you will be using your cable for. Here are some ideas:
- Connecting a Thunderbolt display? Buy an active Thunderbolt 3 cable rated for 40Gbps, with enough length to position it where you want it. Use it for Thunderbolt peripherals.
- Transferring data to your USB 3.1 gen 2 external drive? Buy a USB 3.1 gen 2 cable rated for 10Gbps. Most short Thunderbolt cables of around 1.5 feet will also work, but check first.
- Charging your new smartphone at 3A? If you’re not using the cable for data transfer, any USB 2.0 cable with a Type-C connector will do (pick one that won’t fry your devices).
Then there’s the small issue of adapters. Some early Thunderbolt 3-compliant accessories, like adapters for Ethernet or HDMI ports, are not supported by the latest MacBook Pro. macOS will block some peripherals if they are not explicitly supported.
If you’re buying an adapter specifically for use with your Mac, it’s worth going out of your way to ensure it’s compatible with macOS. That means buying Apple’s first party products, buying your peripherals from an Apple Store, or searching the web and asking around before you buy.
Wired vs. Wireless: The Future of MacBook Ports
Cables can ruin the sweetest of setups. The confusion between USB-C, USB 3.1 and its poorly-named iterations, and Thunderbolt 3 doesn’t help. But for the foreseeable future, they’re here to stay, and we’ll have to live with it.
On the plus side, many once-wired peripherals and gadgets are now totally wireless. The latest smartphones can charge wirelessly, wireless keyboards and mice are the norm, and a new Wi-Fi standard is introduced every few years that pushes network speeds ever higher.
Until the wireless future arrives, you’ll just have to manage that cable clutter in smarter ways.
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