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I have a bunch of USB A to Mini B cables and a single USB A to Mini A cable. I have lost track of where they come from. The two types both look exactly the same with the USB A side having a white plate inside and the shape of the Mini plugs are the same too. So the only difference is that the Mini B plugs are black inside and the Mini A plug is white inside, like the plugs shown here, but my Mini A looks exactly like a Mini B except that it's white.

What is the difference between my USB Mini B and Mini A cables? Do they have the same performance when plugged between my external hard drive and my computer? If not, which type would be better and how?

Should I trust the shape or the color? Because, again, my Mini A plug looks exactly identical to a Mini B plug except for its white-colored plate inside. So could it be that my Mini A is actually just a white-colored Mini B?

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USB specs defined two types of Devices at first. A devices, i.e. Hosts like your pc, and B Devices, i.e. Peripherals like a printer. At first, only standard size existed. Then mobile devices needing a smaller connecter, Mini-B was created. It is still for Peripherals only. Then OTG was added, creating the need for Mini-A (Miniature Host) and Mini-AB (Mixed, OTG device).

So Standard A Male to Mini B Male cables are for use from a Standard Host, to a Mini Peripheral. I.E. Your PC to a Cell phone.

Now, A Mini-A Male to Standard A FEMALE is allowed, as an adaptor, for OTG purposes. Mainly hooking up a standard device to a OTG host. Fairly common now. I have had tablets and phones that came with them in the box. A Mini-A Male to Standard A Male is non-standard as all heck.

The color of the connector on the cable is also defined within USB Specs.

Notably, USB Mini is depreciated and has been replaced by USB Micro for years now.

http://www.usb.org/developers/onthego/london/OTG_mechanical.pdf for an entire breakdown (simple to read) on the cable connector setup, as presented by the USB Implementers Forum.

  • Is an external hard drive with its own power source an A device or a B device? As it says on Wikipedia "only the A-type socket provides power. There are cables with A-type connectors on both ends, but they should be used carefully." But I guess I still should use a standard A Male to Mini B Male between my powered PC and powered external HDD. Is there any case with external HDDs where I should use standard A Male to Mini A male? – randwa1k Oct 21 '14 at 2:06
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    A Hard Drive with its own power source is a Self-Powered Device, just like Hubs. And no, not according to the USB specs. I mean, mini A and mini B cables are wired the same and the difference is just the physical shape, but its non-standard to have a mini-a connector on anything that is not OTG compatible. – cde Oct 21 '14 at 2:12
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The difference only matters for On-The-Go applications, i.e. special cases when a device such as a printer or cellphone is acting in a "host" role rather than its usual "peripheral" role. For your purpose, as long as the cable fits it will work and perform equally well to any other.

  • That is not correct - USB OTG requires the use of micro-A/B/AB plugs/receptacles. USB mini is not supported. – RJR Oct 20 '14 at 4:46
  • @RJR that is 100% wrong. OTG existed on USB Mini as well. – cde Oct 20 '14 at 4:54
  • @cde not according to the specification: usb.org/developers/onthego/USB_OTG_and_EH_2-0.pdf - paragraph 3.1.1. – RJR Oct 20 '14 at 5:03
  • @RJR uhh... Revision 1.3 December 5, 2006 Refer to the USB 2.0 specification and the Micro-USB supplement for all connector and cable assembly information and replace mini- connector references with micro-connector references. Your blindly reading a document without regard to age, on a question that is age specific. – cde Oct 20 '14 at 5:16
  • I stand corrected - I didn't realize anyone implemented OTG that long ago. Based on the OPs statement that "my Mini A looks exactly like a Mini B except that it's white." I would assume though that they're either all mini-A or all mini-B. – RJR Oct 20 '14 at 6:25
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See the picture below; Mini-A left, Mini-B rightenter image description here

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If the plugs look exactly the same (shape - not color) then they are either both mini-A or both mini-B.
Mini A and Mini B are distinctly different: https://en.wikipedia.org/wiki/USB#Mini_connectors

Note that a mini-AB receptacle accepts both mini-A and mini-B cables. So if your cables really have different plugs than they can be used interchangeably only if all your devices have mini-AB receptacles.

In summary: no difference. I suspect your mini-A cable is actually a USB Type-A to USB Mini-B cable.

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