HN Debrief

WhatCable: Know what your USB-C cable can do

  • Hardware
  • Developer Tools
  • Consumer Tech

WhatCable is a utility for checking what a USB-C cable reports about its capabilities, aimed at the very common problem of having a drawer full of identical cables with wildly different behavior. In practice, people are using it to answer simple questions like "will this do data at all", "is this only USB 2.0", and "does this cable advertise higher power delivery". Several people immediately asked for Linux and Windows support, and those already exist through separate repos and a Windows port. ChromeOS also exposes similar cable and port details through firmware support, which helps explain why this sort of introspection is possible on some systems and not others.

Use tools like this to inventory and label cables you already own, especially to separate USB 2.0, higher-speed, and power-capable cables. Do not treat the result as proof that a cable truly meets its advertised USB4 or high-wattage spec unless you bought from a reputable vendor or tested it with serious lab equipment.

Discussion mood

Mostly positive and practical. People like having a simple way to identify mystery USB-C cables, but the strongest technical voices insisted that neither this app nor cheap consumer testers can verify high-speed or high-power claims, only report what the cable and host say.

Key insights

  1. 01

    Platform support depends on firmware hooks

    Support is less about the app itself and more about whether the operating system and firmware expose USB-C and eMarker details. ChromeOS already has substantial built-in support through its firmware stack, and the Linux ports are effectively wrappers around whatever the machine can surface. That means results can vary sharply by laptop and controller even when the software looks identical.

    Before adopting a cable inventory tool across a fleet, test it on the actual hardware models you use. Capability here is a property of the whole platform, not just the app binary.

      Attribution:
    • nedrichards #1
    • haunter #1
    • VorpalWay #1
    • SweetSoftPillow #1
  2. 02

    Low-power Macs may not interrogate cables

    Mac hardware appears not to query cable details in some low-power cases, especially when the charger is 60 watts or less. That makes the absence of reported cable metadata ambiguous. You may be looking at a host behavior limit rather than a cable that lacks an eMarker or capabilities.

    If a Mac shows little or no cable data, retry with a higher-power charger or another host before concluding the cable is uninformative. Build that caveat into any support docs so people do not mislabel good cables.

      Attribution:
    • lxgr #1
  3. 03

    Cheap testers help with failure screening

    Even the people who accepted that cheap testers are not certifiers still found them handy for maintenance. Wiggling a cable while watching continuity indicators can expose intermittent connector failures, and one commenter pointed out that the paid version of WhatCable tracks a cable's history over time. That shifts the value proposition from proving compliance to catching degradation and flaky real-world behavior.

    Use low-cost tools to screen for intermittent faults and maintain a shortlist of trusted cables. For travel kits and support benches, that is often more valuable than chasing formal compliance numbers.

      Attribution:
    • kbouck #1
    • mrexroad #1
  4. 04

    Many useful USB-C cables are only USB 2.0

    A lot of cables sold and shipped today are perfectly valid USB-C cables with power delivery and USB 2.0 data only. They are thinner, lighter, and fine for keyboards, mice, and charging, but they get mislabeled or buried in search results when you actually need SuperSpeed. The confusion comes from treating "USB-C" as a performance promise when it is only the connector shape.

    Label cables by actual role, not connector type. Keep lightweight USB 2.0 plus power-delivery cables for low-bandwidth gear, and separately stock known-good full-featured cables for displays, docks, and storage.

      Attribution:
    • pdpi #1
    • lxgr #1

Against the grain

  1. 01

    This mostly reads claims, not reality

    The skeptical case is that consumer software and cheap cable gadgets are fundamentally reading eMarker data and basic continuity, not measuring whether a cable truly meets its speed or power claims. Since manufacturers can program eMarkers inaccurately, the output can be no better than the cable's own self-description. If you need real assurance on USB4 or top-end power, the only credible path is certified cables from reputable vendors or expensive lab gear.

    Do not use app output as procurement evidence or a compliance check for premium USB-C accessories. For anything business-critical, buy from trusted brands and standardize on a short approved list instead of trusting self-reported cable metadata.

      Attribution:
    • traceroute66 #1 #2 #3
    • LoganDark #1
    • ssl-3 #1
    • nerdsniper #1
  2. 02

    Purging bad cables beats classifying them

    Several comments pushed back on the whole cable-taxonomy project. If you have a pile of cheap USB-A to USB-C or weak USB-C cables, keeping them around creates recurring support and travel friction. The cleaner strategy is to discard anything that cannot do data, keep only a few trusted exceptions like deliberate charge-only travel cables, and stop paying the mental tax.

    Treat low-end cables as consumables, not assets to manage forever. A smaller, cleaner set of known-good cables will save more time than building a perfect catalog of questionable ones.

      Attribution:
    • kccqzy #1
    • ssl-3 #1 #2
    • selicos #1

In plain english

CarPlay ↩
Apple's system for showing iPhone apps and controls on a car's built-in display.
ChromeOS ↩
Google's operating system for Chromebooks, built around the Chrome browser and a Linux-based system.
eMarker ↩
An electronic marker chip inside some USB-C cables that reports the cable's claimed capabilities such as supported power or data rates.
firmware ↩
Low-level software that runs hardware components and sits below the main operating system.
Power Delivery ↩
A USB standard, often shortened to PD, for negotiating higher power levels over USB-C cables and chargers.
SuperSpeed ↩
A USB branding term for higher-speed data modes above USB 2.0.
USB 2.0 ↩
An older Universal Serial Bus data standard with a maximum signaling rate of 480 megabits per second.
USB-C ↩
A reversible USB connector standard that can carry data, video, and power over one port.
USB4 ↩
A high-speed Universal Serial Bus standard that can carry very fast data and display traffic, and whose cable performance is much harder to verify.

Reference links

Alternative implementations and ports

ChromeOS and firmware internals

Cable testing limits and lab equipment

CarPlay and Android Auto workarounds