My MacBook Pro Retina 15 Inch (Mid 2015) running macOS Monterey (12.6.7) has 2 Thunderbolt Ports. Per System Information, Hardware, they are Thunderbolt/USB4. How can I connect an external USB-C Hard Disk Drive to these ports for Time Machine use?

MushroomEater wrote:

My MacBook Pro Retina 15 Inch (Mid 2015) running macOS Monterey (12.6.7) has 2 Thunderbolt Ports. Per System Information, Hardware, they are Thunderbolt/USB4.

Those are Thunderbolt 2 ports. Ignore the USB4 part of the System Information heading. Your MBP's ports are not USB4 ports. It's just that USB4 is based in part on TB3 technology, so the people who designed the System Information application found it useful to show Thunderbolt and USB4 information under the same heading.

How can I connect an external USB-C Hard Disk Drive to one of these ports for Time Machine use?

With the aid of a Thunderbolt dock that has USB ports.

Thunderbolt 2 docks are extremely unlikely to have USB-C ports, but that's OK. Unless your drive depends on USB-C Power Delivery, plugging a "USB-C" drive into a "USB-A" dock port would only require a simple adapter. The bigger problem there is that nobody makes Thunderbolt 2 docks any more; you'd have to find a used one.

Another possibility would be to plug in a Thunderbolt 3 dock, with the aid of Apple's $50 Thunderbolt 3-to-2 adapter. NOTE: Thunderbolt dock, not USB-C dock or hub. You'd want a dock whose upstream link did not have a permanently-attached cable (since the Apple adapter has a TB3 plug).

However, that MacBook Pro has two USB-A (USB 3) ports. It seems like it would be easier and cheaper to plug your drives into those ports (or into USB hubs attached to those ports) than to mess around with Thunderbolt 2 just to get a USB port or two.

A 2015 laptop only has Thunderbolt 2 ports which use the mini-Display Port connector. It also has the traditional USB 3 ports with USB-A style connector.

A USB-C hard disk is probably not using the Thunderbolt protocol, but instead is using the less expensive & more common USB3 protocol. Check the symbol next to the USB-C port on your external drive. If the symbol looks like a trident, then it is using the USB protocol. If the symbol is a lightning bolt, then it supports the Thunderbolt protocol.

If the external drive is using the USB protocol (trident symbol or no symbol), then you need the Apple USB-C Thunderbolt 3 to USB-A Adapter.

If the external drive is using the Thunderbolt protocol (lightning bolt symbol), then you will need to use an Apple USB-C Thunderbolt 3 to Thunderbolt 2 Adapter along with the older style Thunderbolt 2 cable with mini-Display Port connectors.

If you are unsure of the protocol of a device, then check the user manual for the product.

FYI, USB-C is the name of the connector style and has no other meaning (it is a terrible name). A device with a USB-C connector can support the USB protocol or the Thunderbolt protocol. Most external devices will only be using just one of the two protocols. Your laptop is unique where most Apple USB-C ports on Apple computers support both the Thunderbolt protocol and the USB protocols (there are a few exceptions though, so read the product documentation).

A device which uses the Thunderbolt protocol must connect to a Thunderbolt port, and a device using the USB protocol must connect to a USB port. Things are a little tricky when USB-C ports are involved because you must learn what protocol(s) each USB-C supports on each of the devices.

You need a good USB to USBC cable to connect to the external disk.

This is based on the assumption that 1. Your Mbp is 2015, not 2016 or later 2. Your external disk uses USBC not thunderbolt3 (TB3/4 products are quite expensive and relatively rare).

However, if the disk is TB3, AND is self powered, then you can get Apples TB3/TB2 adaptor and use the TB2 ports of Mbp. This will give you higher (up to 4x) bandwidth.

Here's one example of a USB-C (female) to USB-A (male) adapter. This is the reverse of the direction that people normally go, but in your case, you might be trying to connect a USB-C drive to a USB-A port.

https://www.amazon.com/TRIPP-Adapter-Converter-USB-C-U329-000/dp/B07GX2XFYJ/

Note the parts of the description that mention "5 Gbps Data Transfer" and "900 mA Power Output". Some cheap charging cables and adapters might not support USB 3 data transfer rates, or might not carry USB 3 levels of power (for powering accessories like flash drives, card readers, and portable hard drives).

HWTech wrote:

A 2015 laptop only has Thunderbolt 2 ports which use the mini-Display Port connector. It also has the traditional USB 3 ports with USB-A style connector.

If the external drive is using the USB protocol (trident symbol or no symbol), then you need the Apple USB-C Thunderbolt 3 to USB-A Adapter.

Does that adapter work when the USB-C end is plugged into a USB-C peripheral (such as a hard drive), rather than into a USB-C (USB or Thunderbolt 3) host port? And the USB-A end is plugged into the computer?

Apple doesn't say that it will work when used in this fashion.

Servant of Cats wrote:

HWTech wrote:

A 2015 laptop only has Thunderbolt 2 ports which use the mini-Display Port connector. It also has the traditional USB 3 ports with USB-A style connector.

If the external drive is using the USB protocol (trident symbol or no symbol), then you need the Apple USB-C Thunderbolt 3 to USB-A Adapter.

Does that adapter work when the USB-C end is plugged into a USB-C peripheral (such as a hard drive), rather than into a USB-C (USB or Thunderbolt 3) host port? And the USB-A end is plugged into the computer?

Apple doesn't say that it will work when used in this fashion.

It might work. I see that Apple does not describe it as a Thunderbolt adapter, but as a USB-C one. (If it had been relying on Thunderbolt on the USB-C side, then most USB-C (USB) drives would not have been able to speak the protocol it was expecting.)

Mea culpa.

There are some docks, that you can plug in at your Thunderbolt port to make it more ports, some have Usb C but they're rare find these days

With a simple passthrough adapter. They're sold all over the web ... Apple has a good one.

HappyL wrote:

Your external disk uses USBC not thunderbolt3 (TB3/4 products are quite expensive and relatively rare).

"USBC" is not a communication protocol. USB-C is a connector type. You should have just said "USB3" or "USB".

If you are going to repeat what others have already suggested here, then please make sure your information is accurate.

Servant of Cats wrote:

HWTech wrote:

A 2015 laptop only has Thunderbolt 2 ports which use the mini-Display Port connector. It also has the traditional USB 3 ports with USB-A style connector.

If the external drive is using the USB protocol (trident symbol or no symbol), then you need the Apple USB-C Thunderbolt 3 to USB-A Adapter.

Does that adapter work when the USB-C end is plugged into a USB-C peripheral (such as a hard drive), rather than into a USB-C (USB or Thunderbolt 3) host port? And the USB-A end is plugged into the computer?

Apple doesn't say that it will work when used in this fashion.

I believe I used that adapter in the reverse configuration several years ago.

Thanks for mentioning the dock options.