Category:Legacy USB 2 cables

Hi, I'm a bit puzzled by this category. Is there a definition of 'legacy' in this context, please? Thanks. Mike Peel (talk) 08:00, 17 May 2025 (UTC)

Oh yes: All USB connectors that are not Type‑C are “legacy” and have been referred to exclusively as such in all USB Implementers Forum materials beginning with the documents defining Type‑C in 2014. The entire purpose of Type‑C is to obviate all other USB connectors, replacing all of them, hence “legacy”.

“USB 3.1 Legacy Cable and Connector Specification”

2017

https://www.usb.org/document-library/usb-31-legacy-cable-and-connector-revision-10

“Universal Serial Bus Type-C Cable and Connector Specification”

2024

https://www.usb.org/document-library/usb-type-cr-cable-and-connector-specification-release-24

“Universal Serial Bus 3.2 Specification”

2022

https://www.usb.org/document-library/usb-32-revision-11-june-2022

“Universal Serial Bus Type-C Connectors and Cable Assemblies Compliance Document”

2021

https://www.usb.org/document-library/usb-type-cr-connectors-and-cable-assemblies-compliance-document-rev-21b

“Universal Serial Bus 3.1 Legacy Connectors and Cable Assemblies Compliance Document”

2018

https://www.usb.org/document-library/universal-serial-bus-31-legacy-connectors-and-cable-assemblies-compliance-document

Stephan Leeds (talk) 08:20, 17 May 2025 (UTC)

I do intend to note the distinction as appropriate on each applicable Category page; just haven’t managed to get that done yet. Stephan Leeds (talk) 19:02, 17 May 2025 (UTC)

THanks for the explanation, and apologies for the slow reply, I'm currently travelling. I'm worried that 'legacy' is likely something that will change over time, it might be better to refer to these as types A/B/mini/etc. more specifically as that will be (presumably) fixed. The rename of Category:Plug-in USB power supplies with legacy Standard-A receptacles to Category:Plug-in USB power supplies with Standard-A receptacles looked good to me, as an example. Thanks. Mike Peel (talk) 05:04, 23 May 2025 (UTC)

I share and agree with your concern about the term changing over time (specifically when and if the term USB continues to whatever replaces the Type‑C connector); the awkward thing that weighs against that is that the only reason we still have this absurd mess of bad connectors is that people think that Type‑C is just yet another connector adding to the mess, missing the point that its entire purpose is to replace the mess. I hate to put anything in the data structure that will need to change, but given the fraction of files regarding USB that are misnamed or are otherwise misleading (I’ve requested deletion of several that misinformed, e.g. with incorrect pinouts), marking the distinction between the modern connector and the mess that was supposed to go away long ago seems compelling. I’m not committed to that position—it was just clear that the info about USB connectors was a mess and that was the judgement call I made for the time being in cleaning it up. There’ve been several that I made and reversed in the process as well.

Maybe you have ideas on this related issue?: On the “plug-in” things I’m hoping to find a better way to name that, something that’s clear, coherent, and searchable but consistent with other “chargers” like the twelve-volt car things (which plug into, or plug in to, cars, depending on dialect), but the common English terms for these things are messy: mains is accurate but foreign to some speakers (Apple’s marketing team chose AC adapters), there is no common and accurate term for the car things that I can find, power supply is odd but charger is inaccurate because things without batteries are powered by these things too. Stephan Leeds (talk) 18:50, 23 May 2025 (UTC)

Category:Prohibited USB adapters

Hi again, and thanks for your categorisation work! I'm also puzzled by this category, though - what does 'prohibited' mean in this context, who's doing the prohibiting, and what's prohibited in File:At London 2024 055.jpg? (it's just a USB-C to -C cable, and a USB-A to -C adapter...) Thanks. Mike Peel (talk) 06:17, 2 July 2026 (UTC)

Ah! It’s the Type-C-receptacle-to-Standard-A-plug adapter that’s the problem. I had the same thought when I marked it—I knew it was prohibited because the USB-C standard explicitly prohibits all but the two adapters it describes and this is not one (and the USB standards in total only allow three adapters—those two and the Standard-A-receptacle–Micro-A-plug one), but I had to think about why this one is dangerous. It’s because it would allow a cable–adapter assembly with a Type-A plug at each end, or a Type-A plug at one end and a Type-C plug at the other that isn’t electrically marked as the B end. In other words, it allows two hosts to connect to each other and, aside from not working, a host with a Type-A receptacle isn’t (required to be) designed to handle being connected to another host—with its VBUS—without damage. (There is, however, the one allowed A–A debugging cable, with a modified USB 3 Standard-A plug at each end, which is safe only because the power and legacy data contacts aren’t connected.) In short any adapter with a C receptacle and a legacy plug is prohibited because it breaks the requirement that every cable have an A end and a B end. In any cable with a Type-C at one end and a legacy plug at the other the Type-C plug is electrically marked as logical A or B, to complement the legacy plug, so the device it’s plugged into knows how to behave (including just ignoring the connection if it can’t take the role the plug requires).

I regret that I’ve let this work sit unfinished for so long and I’m hoping to get it into a more consistent state soon. Stephan Leeds (talk) 21:56, 2 July 2026 (UTC)

Oh, I still didn’t answer your question because I forgot to paste a couple links and to mention that those two docs cover adapters explicitly:

The current cable and connector specs are all in two documents:

Type-C: https://usb.org/document-library/usb-type-cr-cable-and-connector-specification-release-25

legacy: https://www.usb.org/document-library/usb-31-legacy-cable-and-connector-revision-10

I actually always carry a (prohibited) C-receptacle–Standard-A-plug adapter with me so that I only need to carry one (C–C) cable for everything and can connect to a Standard-A receptacle if I need to, and I just have to know not to make a cable assembly with a Type-A a each end. Since the adapter’s C receptacle claims the A role the assembly works fine as long as it’s connected to only a C–C (or C–B) cable. Stephan Leeds (talk) 22:22, 2 July 2026 (UTC)