When I built my computer I had a USB 3.0 cord where one side looked like a normal USB to stick into a USB port but the other end has this blue thing:

USB 3.0 weird side

Where do I stick that in?


3 Answers 3


That is a 19 pin USB header connector. The header connector would plug into your motherboard, and then you could add internal USB devices. I have one which I believe is used for a card reader and I think I also had to connect a header to enable a second USB 3.0 port that is built into my case. I'd have to actually look in my case to double check what I used it for.

enter image description here

  • 4
    I just assembled a PC, and the USB 3.0 front plugs of the case were connected to the mainboard by exactly the same cable, as shown in the photograph. Aug 18, 2017 at 11:26

That is a male USB3 (always colored blue with 19 pins) header cable. I don't know why it would have a male USB connector at the end of it though.. Perhaps it's designed for direct USB access from another host or connecting USB components internally, like a USB port on your case. I suspect OP has misidentified the connector at the end of the cable. It is most likely female because there is very little use for an internal male connector.

enter image description here

Here is an image of what I suspect to be OP's cable actually looks like:

enter image description here

  • Those typically break out to two plugs, I have one in my system since my front panel USB 3 plug ends in a USB 3,0 male. Other plug's vaguely useless
    – Journeyman Geek
    Aug 21, 2017 at 12:12

As other answers have said that is a connector for plugging into a USB3 motherboard header.

A cable from that to USB 3.0 plugs makes no sense. I expect you have misidentified what is on the other end of the cable and your cable actually has sockets on the other end. Plugs and sockets can look quite similar if you aren't looking carefully.

If I'm right the purpose of that cable is to allow the motherboards USB3 header to be connected to the front panel ports on older cases. When USB3 was first introduced there was no front panel header for it and cases with front USB3 ports came with regular USB3 plugs intended to be plugged into sockets on the rear panel.

Another possibility is that the picture you posted doesn't actually match the connector you have (I notice it's a picture taken from DX, not a picture of your cable). You may see a cable with USB3 plugs and a male header connector for the opposite problem of connecting a newer case to an old motherboard.

  • 5
    it makes sense if thats how the case manufacturer designed the external port interface, especially if they wanted to get around a design patent or licensing fee of some kind Aug 15, 2017 at 23:56
  • @RichieFrame I think it was simply the case that Mobo manufacturers weren't including internal USB 3.0 headers on all but their highest end mobos when it first came out, so case manufacturers were using the cable method to make sure that anyone could use USB3.0 in their new case regardless of the mobo. It's also a good fallback as you can simply plug it into a USB 2.0 port and it'll still function.
    – SGR
    Aug 16, 2017 at 10:05
  • As far as I remember the internal header didn't show up at all (even on high end boards) until some time after USB3 was introduced.
    – plugwash
    Aug 16, 2017 at 15:43

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