A nearly perfect USB cable tester

https://blog.literarily-starved.com/2026/02/technology-the-nearly-perfect-usb-cable-tester-does-exist/

by birdculture • 4 months ago

300 171 4 months ago

blog.literarily-starved.com

Onavo2• 4 months ago

I just want one that tells me the maximum voltage and current supported by a USB C cable.

wolfi12• 4 months ago

there are several: one that is moderately priced and which I consider myself to buy is the JOY-IT UM120

Onavo2• 4 months ago

Thanks, why do you prefer that particular model?

contingencies• 4 months ago

Got this recently for USD$3 on sale: https://www.aliexpress.com/item/1005006848187940.html

fmajid5• 4 months ago

The Treedix will tell you that, as it is a feature of the eMarker chip (no chip means 60W).

SAI_Peregrinus5• 4 months ago

Assuming the chip isn't fraudulently added. Like in the article, some manufacturers are shady & will sell cables with e-marker chips for capabilities the cable can't actually support.

Gigachad6• 4 months ago

The thing that has been bothering me for a while is that the USB spec allows for software detection of capabilities. You can read the emarker data and see the supported protocols, speeds, voltages, etc.

But there is not standard for usb controllers to present this data to the OS. So it’s stuck in the low level firmware and never passed up. In theory we could have a popup box that tells you that both your computer and other device support higher speeds/more power, but your cable is limiting it.

Apple seems best able to do this since they control the hardware and OS, yet they aren’t doing it either. Users are just left to be confused about why things are slow.

avian• 4 months ago

In theory we could have a popup box that tells you that both your computer and other device support higher speeds/more power, but your cable is limiting it.

I'm pretty sure my old Dell XPS laptop with Windows 10 had pop-ups just like this.

"This device can run faster" or something.

LoganDark• 4 months ago

Even Apple now has one of those, when you plug something into the USB 2 port on the MacBook Neo.

Vogtinator• 4 months ago

AFAIK that's just when plugging in a USB 3 device into a USB 2 port or using a USB 2 cable.

imglorp• 4 months ago

I wonder if it's possible for a regular machine with two high speed ports to do a cable test by itself. Maybe it can't test all the attributes but could it at least verify speed claims in software?

colechristensen• 4 months ago

I strongly suspected my old xps had nonstandard things going on with its USB C charger

graemep3• 4 months ago

I suspect most users do not even realise things are slow.

TeMPOraL4• 4 months ago

Oh, they very much do. But like with everything in technology, they can do fuck all about it, so they resign and maybe complain to you occasionally if you're the designated (in)voluntary tech support person for your family and friends.

Regular people hate technology, both for how magical and how badly broken it is, but they've long learned they're powerless to change it - nobody listens to their complaints, and the whole market is supply-driven, i.e. you get to choose from what vendors graciously put on the market, not from what the space of possible devices.

QuantumNomad_• 4 months ago

On iPhone, when connecting an external MIDI device via USB, the phone told me that the device was drawing too much power and would be disabled.

I don’t know if they check that via USB protocol, or if they are measuring the actual power draw on the USB port.

In order to use the device, I had to connect it via an externally powered USB hub.

vladvasiliu2• 4 months ago

But there is not standard for usb controllers to present this data to the OS. So it’s stuck in the low level firmware and never passed up. In theory we could have a popup box that tells you that both your computer and other device support higher speeds/more power, but your cable is limiting it.

There is. I used to use a KVM with USB 2 ports connected to my PC's USB 3 port, to which I connected a monitor with integrated USB 3 hub to drive my keyboard and mouse. Windows would show a popup every time telling me that I should use a faster cable.

There are also popups telling me that my laptop is connected to a "slow" usb-c charger.

Forgeties792• 4 months ago

I have seen these kinds of notifications on occasion but they are far from the norm.

wholinator2• 4 months ago

I've used all manner of archaic usb cables for data transfer when in a pinch and windows has never shown me anything at all. Could it be the external device you were connecting to triggering the windows notification?

bdavbdav2• 4 months ago

That’s quite a simplistic one unfortunately - USB 2 and 3 use different controllers in the PC, which it can indeed detect. The sub-flavours of 3/4 less so.

Barbing3• 4 months ago

Perhaps someday it will earn the same level of importance as charging; iOS 26 calls out slow chargers on their iPhones, so you can run to the Apple Store and buy a fast one!

They probably have to weigh potential new hardware sales against added complexity. I have counterpoints too but: I believe they try to protect users’ mental models of their ecosystem (which perhaps I appreciate when I don’t notice, and can’t stand when something is uncustomizable). Like there are enough variables they don’t trust us with as it is.

tredre3• 4 months ago

iOS 26 calls out slow chargers on their iPhones, so you can run to the Apple Store and buy a fast one!

You jest but that notification (it's been a thing on Android for at least 8 years, and on thinkpads for at least 10) has been very helpful to me. Sometimes the negotiation just fails and being told is helpful. Sometimes the charger lies about its specs and once again it's helpful to have a hint, rather than expect everybody to systematically have usb testers on hand.

pseudohadamard6• 4 months ago

Does it matter, for anyone other than hardcore geeks? All the OS would care about is how much power can it deliver and what data speed it provides, not whether the exception handling on page 4,096, section 4(a)2.1, paragraph 4 of the spec, has been implemented.

prism56• 4 months ago

Android must have this in some form. My Pixel phone with a third-party app can show the voltage and current mode selected via the PD protocols.

Using DevCheck might show 2.2A/9V as an example.

EnnEmmEss• 4 months ago

It's fun to see the Treedix tester come up on HN. I got one a few months back and have quite enjoyed using it. One thing which I did find interesting was that one of the cables had the emarker data lie. IIRC, the emarker data would suggested it supported much higher speeds and wattage than it did. Fortunately, the other testing screens successfully detected it only had USB 2.0 wires even though it claimed to support 40 GB/s.

Modified3019• 4 months ago

I’ve had one for a while as well. I don’t use it often, but frankly I couldn’t sort my cables without it.

amelius• 4 months ago

I want one that sends a pseudorandom data stream and tells me the bit error rate.

the_biot• 4 months ago

Yup, that's the sort of thing that's typically missing from cable testers. I have a USB cable that normally works fine, but introduces errors when doing full blast USB 2.0 bulk transfers. I keep it around just in case I ever come across a tester that can show me this in hard numbers.

HDBaseT• 4 months ago

Products that do exactly that do exist, although are prohibitively expensive. [0]

It is difficult to send 10Gbps, 20Gbps, 40Gbps or even 80Gbps, then receive it, then validate it.

[0] https://www.totalphase.com/products/advanced-cable-tester-v2...

specialist• 4 months ago

Yes and: If a cable has any faults, of any kind.

I can't believe I'm still swapping cables and ports, trial and error, trying to determine if the cable, the port (eg iPhone's charging port), or both, are failing.

Not knowing the USB specs; I assume each head of a cable can do a loop back test, determine if can even see its other head, etc.

atoav6• 4 months ago

One thing to realize is that especially for high resolution video cables these cheap testers can't really deliver. The way to test them is a eye diagram (see: https://incompliancemag.com/eye-diagram-part2/ ) and testers with that capsbility cost upwards of 10.000 Eurodollars.

jmalicki5• 4 months ago

So you're saying there is something to audiophile grade HDMI cables?

HPsquared• 4 months ago

With digital signals and ECC, the cable need only be "good enough" to get perfect data transfer through the system.

scq• 4 months ago

No. What it can affect though is the bandwidth of the cable, meaning e.g. for HDMI cables, they might not support higher resolutions or framerates. If it's on the border you might see random disconnects or screen blanks.

The quality degrading is not something you will see, as it's a digital protocol.

"Audiophile grade" HDMI cables are likely to just be a Shenzhen bargain-bin special with some fancy looking sheathing and connectors. I would trust them less than an Amazon Basics cable.

atoav6• 4 months ago

No. What I am saying is that it is hard to test the quality of a 8K 240Hz 4444 video cable without having a device that can send and receive this or even higher.

If you send bits across a line fast enough you're grtting into the territory of RF electronics, with wrong connector or conductor geometry you will get echos on the line and all kind of signal loss. A good digital protocol should keep this at bay with error correction and similar mechanisms, but if you want to know what the good cable is on a better than binary scale of works/does not, you need to look at these things.

SAI_Peregrinus5• 4 months ago

Keysight are nice enough to provide prices on their web site for all their cheaper equipment. I priced out a setup for USB 2.0 eye diagram compliance testing on their site in this comment¹ and it's more like $40,000 than $10,000.

¹https://news.ycombinator.com/item?id=47568399

atoav6• 4 months ago

I said 10k because I think I saw a specialized product just for HDMI starting at roundabout that price bracket once mentioned in a youtube video, csn't really remember the brand, but it was relatively unknown in terms of test equipment. More generic (and flexible) equipment like the one mentioned will indeed tear a deeper hole into your pocket, but comes with its own perks.

Eisenstein3• 4 months ago

Hopefully they used connectors with a high mating cycle rating.

seanalltogether• 4 months ago

I wasn't surprised to learn that when Linus Tech Tips released those new usb-c cables, that they all sold out almost instantly. They put their entire reputation on the line to claim (and label) the exact capabilities of their usb cables. Isn't that all we really want?

bryanhogan• 4 months ago

The video: https://youtu.be/OT_iyvOy0Tk

Of course they are advertising their own new USB cable, but as someone who didn't know much about USB cables I find it quite interesting.

AceJohnny2• 4 months ago

They lost me at "our conductors are coax!". USB is designed around differential signaling, which is what twisted pair excels at.

Dylan168072• 4 months ago

Twisted pair is good but it only gets your losses so low at these speeds. Keep in mind that USB cables have a very small budget for signal loss, and at 40Gbps they're carrying frequencies 25x higher than 10gig ethernet.

ChrisMarshallNY3• 4 months ago

This isn't a Beagle. When I first read the headline, I was hoping that it would be more than a smart continuity tester.

It seems to be a more comprehensive "Make sure the lines go where they are supposed to" tester. Looks pretty good.

But the devices that test things like transmission speed, are a lot more expensive.

I think that many of the issues that this device tests, can be mitigated by simply buying cables from reputable sources.

Liftyee2• 4 months ago

Once in the realm of signal integrity, it's true that the price goes straight into lab grade levels.

Even in my reputable cables, there are a couple with suspicious continuity issues. I wonder if this could find them.

You could probably build a data transfer tester using an FPGA and some signal processing.

mwexler• 4 months ago

Wasn't aware of this level of testing. $1300 for a Beagle is a big step up.

ChrisMarshallNY3• 4 months ago

That's a cheap one. Some of the analyzers can go into 5 figures.

Don't forget the speeds at which modern serial interfaces go. Being able to look at the data, at that speed, requires some serious kit.

Raed6672• 4 months ago

As someone who really doesn't care about learning the details, and just want one USB-C cable that does it ALL to put in my backpack what should I buy ?

publicmail• 4 months ago

A thunderbolt cable

Raed6672• 4 months ago

Would it work with USB-C screens and projectors ?

bombcar• 4 months ago

And to be precise, a nice, high quality thunderbolt cable from a reputable manufacturer like Apple or OWC. Protect the cable as it will have been expensive, but it will work very well.

mystifyingpoi• 4 months ago

This is the solution, but it is 1) expensive and 2) Thunderbolt cables are quite short compared to regular USB-C.

Gigachad6• 4 months ago

You don’t really want that. A thunderbolt cable is both stiff and expensive. They only really make sense to leave attached to the back of a monitor or dock.

What would work better is a flexible 100w+ usb3 cable. You can’t do thunderbolt on it but it’s a tiny fraction of the cost and does everything you’d actually need on the go.

If you actually do want it, this is the do everything cable https://www.apple.com/au/xc/product/MW5H3ZA/A

johnwalkr• 4 months ago

At my workplace someone always orders the what they perceive to be the "best" cables. They aren't thunderbolt, they are just oversized with thick braiding. They are all so stiff and heavy you can barely handle a phone while charging without the cable pulling itself out.

mrandish4• 4 months ago

So much this. I have a few different categories of "known good" USB-C cables because one type doesn't fit all my use cases. Sometimes the trait I need is >100w PD charging at 1M. Sometimes I need 80 Gbps dual 4k video at 3M. Other times I need 40 Gbps .5M to a portable NVMe enclosure. USB-C cables I regularly rely on range from $5 to $100 and weight/size varies >3x.

And in my tiny 'go bike bag' for day trips I need one 2M cable that's thin, coils into a tight ball and weighs nothing yet will charge up to 45w and reliably xfer data at up to 5Gbps (USB 3.1) for quick uploads with optional USB-A and Micro-USB adapters at either end (because I still know people with Micro-USB (though it obviously drops to USB2 speeds)).

cmiles74• 4 months ago

I’m sure it’s overkill but I wanted to know how much power my laptop or whatever was actually drawing.

https://iaohi.com/products/aohi-the-future-adonis-usb4-2-0-2...

tom_alexander2• 4 months ago

As an alternative, you could get a stand-alone USB-C power meter which can be used with any cable. That way, when the cable breaks, you don't have to buy a new power meter. Here is an example of one such product (though I've never used this model): https://www.amazon.com/Adapter-Voltage-Current-Extension-Con...

s3p2• 4 months ago

Love this! I got a USB C multimeter and used it to test the output of two dozen chargers. Wanted to see if they supplied the voltage that was advertised. Funny enough, AOHI was the only brand whose chargers actually increased their voltage as my current draw went up. It was like the engineers knew about the resistance in the wire and decided to compensate by upping the voltage slightly.

qingcharles• 4 months ago

LTT did a lot of work to prove their cables do everything they say:

https://news.ycombinator.com/item?id=47561827

(these are what I would buy from a sea of cables, not the cheapest, but far from the most expensive)

Liftyee2• 4 months ago

Brilliant little device. I will be picking one up ASAP!. Didn't know that lying cables were a thing but I have a ton of charge only cables?!

I speculate USB B wasn't included because there are only really two types, 2.0 (regular size) and 3.0 (has an obvious extension on the connector). There also don't tend to be power-only A-B cables because they are usually found on printers, Arduino s, ... And not for charging devices.

Fun fact: A Xiaomi fast charge cable (with orange plugs) has an extra contact on the A end to support USB C PD out of a USB A charger.

dijit14• 4 months ago

I actually purchased one of these as this article has surfaced before.

It’s well worth the hype, I used it to audit all my cables (both for home and work) and it’s amazing how many thick and unwieldy cables are actually terrible for data.

For example I purchased a pair of B&W Px8 S2 noise cancelling headphones, which boast a DAC if you connect via USB-C directly, the cable it came with though was thick but only rated for USB 2.0 speeds. These headphones cost more than AirPods Max, which are themselves considered overpriced, and include comforts like nappa leather; so shipping with a chunky cable that doesn’t even carry decent data feels like a bizarre oversight. Apple’s own USB-C cables manage the same power delivery at less than half the thickness with a woven shell. You’d assume a premium product would at least match that.

Honourable mention to the USB-C cables that ship with Dell Ultrasharp monitors (both pre-USB4 and post). Those support basically everything except Thunderbolt 4 despite being unmarked.

fwip• 4 months ago

Is there any audio you might play that doesn't fit in 400Mbps?

dijit14• 4 months ago

The point isn’t really about audio bandwidth; it’s about the cable being strangely overbuilt for what it actually does.

It’s rigid and thick, like a Thunderbolt 3 cable, yet only supports USB 2.0 speeds and fast charging for a device that doesn’t need fast charging.

Compare that to Apple’s iPhone USB-C cable which is thin, flexible, and supports the same features.

That matters because someone might grab that cable assuming it’s a “better cable”: it came with a £629 product, it’s thick and feels serious, so surely it’s capable. But it isn’t. And there’s nothing marked on it to tell you otherwise.

The whole system ends up relying on presumption, which is exactly the problem the device in the article is solving.

encom2• 4 months ago

No. CD audio is 1,4 mbit. Even increasing the temporal and spatial resolution beyond that, which is audiophile nonsense, will never even approach USB 2 speeds.

Aurornis4• 4 months ago

so shipping with a chunky cable that doesn’t even carry decent data feels like a bizarre oversight.

USB 2.0 can support up to 480 Mbps. It’s more than fast enough for any audio stream you can send to a DAC.

Your headphones don’t need USB 3.0 5 Gbps speeds. USB 3 requires extra wires with different properties that need to be controlled more tightly, which can impact cable flexibility. If your headphones used USB 3 when they didn’t need it that would be one more thing to break and more failure modes for the cable.

A USB 2 cable with fewer conductors was the right choice for this product. The fact that you only got miffed about it when plugging the cable into a tester, not from actually using the product or cable, is good evidence that a USB 3 cable wasn’t needed.

dijit14• 4 months ago

Nobody said the headphones needed USB 3. The point is that the cable is physically thick and rigid (like something you'd expect to carry serious data) but doesn't. Meanwhile Apple ships a thinner, more flexible cable that supports the same USB 2.0 speeds and equivalent power delivery. The cable B&W chose is worse ergonomically for no functional benefit. That's the kind of mismatch the Treedix exposes.

joshvm• 4 months ago

I started buying Belkin TB5 cables which are around $50 a pop. They can easily power a laptop at full load and can stream video at any reasonable resolution/framerate I might need. I've yet to find a need for an NVMe faster than 20 GBps nevermind finding USB4 enclosures, or that the cable supports up to 80. They're also not nearly as chunky as the Dell cables, which are good, but seem to have very rigid shielding.

I keep a few converters for older devices and servers that don't have (m)any C ports, but as far as a consumer "forever cable" goes, TB5 feels close. Certainly the cable's bandwidth is beyond what most people need, unless you're editing 8k video or continually shuffling hundreds of GBs between external disks.

dijit14• 4 months ago

I do something largely similar.

It alleviates the anxiety of knowing what cable does what.

I use Apples Thunderbolt 4 or USB-C cables exclusively: if its white its for charging and low data, if its black its for high data.

I’ve been doing this for a few years, but its really costly as those Apple Thunderbolt cables are crazy expensive.

vladvasiliu2• 4 months ago

Honourable mention to the USB-C cables that ship with Dell Ultrasharp monitors (both pre-USB4 and post). Those support basically everything except Thunderbolt 4 despite being unmarked.

I have one of those. They are thick and unwieldy af. Since I've borked the usb connection on my monitor because of static discharge, I no longer use it and figured I'd repurpose it for my digital camera, for which I used to have a short cable that was sometimes annoying. This cable is so freaking think and hard that it'll move my (admittedly somewhat light) camera on the table.

pseudohadamard6• 4 months ago

There are a bunch of similar testers around that do more or less the same thing, e.g. a the ChargerLab Power-Z range or any number of dodgy third-party Amazon/Aliexpress clones. The one thing that definitely doesn't exist though outside of $1,000-and-up USB diagnostic devices is something to report on which of the 800 different ways the downstream device has screwed things up, including failing a basic cut-and-paste of pullup resistors from the spec coughRaspberryPicough.

After the publicity a few years ago of bad USB-C cables they've been mostly fixed, but what hasn't been fixed is the infinite number of broken downstream USB-C implementations. So your charging problems aren't due to the cable, which is most likely fine by now, but because the downstream device is telling the upstream one that it can't take more than 5V 1A. One sure way to tell the vendor has screwed up is when your USB-C device comes with an A-to-C cable to charge it.

pseudohadamard6• 4 months ago

Just to clarify the above, I'm talking about USB-C PD, not data throughput, on re-reading it the text is a bit unclear.

bArray• 4 months ago

What I'm looking for is a differential signal tester, where you can breakout any arbitrary cable or traces and test the properties of the wire with different frequencies. It should be able to measure interesting properties such as resistance, capacitance, inductance, phase/length difference, wire length, etc.

One of these devices for approximately $100 would sell all day long.

Eisenstein3• 4 months ago

You can do that with a nanoVNA, except for the differential part. Less than $100.

mmastrac• 4 months ago

Can you rewrite the emarker chips?

kotaKat2• 4 months ago

Similarly: Is there a USB-C power delivery adapter to force directionality? I needed to siphon off power from small batteries into a larger pack (that could supply more power out than the small packs) in a power outage. I absolutely could not force my larger power station to accept a charge and it kept pushing power back the wrong direction despite which ends of the cable I plugged in first.

ssl-33• 4 months ago

It's ugly, but yes: https://www.anker.com/products/a8895?variant=45839927509142

That cable has one power input (that is only an input), and two outputs (that are only outputs), and a brainbox in the middle to direct the circus.

If we label the connectors as A, B, and C, then it works like this: A charges B and/or C, and other charging directions are no-op.

The less-complex way is to use a USB A to C cable, if that's appropriate. With these, the A side is always the source and the C side is always the sink.

---

And yeah, it's annoying. I got a cheap lithium car jump starter several years ago with some neat power bank features (like 60W USB PD in/out, on one port). So I plugged it into my phone with USB C at my desk, and discovered that they'd charge eachother seemingly randomly. While changing nothing, I'd look over and sometimes the jump starter would charge the phone, and sometimes the phone would be charging the jump starter. The conglomeration formed a heater, with more steps.

(Back and forth with the same poop, forever.)

kotaKat2• 4 months ago

Ah, yeah, I remember those. That miiiiight work for my use case...

--- (I remember. The poop.)

bean469• 4 months ago

Sucks that there's no USB-B support. Plenty of monitors still use it and many printers do as well

pseudohadamard6• 4 months ago

For older cables there's a guy who's posted a large list of test stats somewhere... ah, here we go, I remember the "long thin resistor" comment: https://www.cs.auckland.ac.nz/~pgut001/pubs/usb_cable.html. tl;dr, you can't go wrong with Anker. Also, there's some absolute garbage out there.

superxpro123• 4 months ago

would an adapter fill the gap until support is added?

trinsic2• 4 months ago

Man. I wonder if my cables are the reason why I cant get reliable transfer speeds above USB3.0 speeds on a new USB-C dock I purchased..

I didn't know there were cable testers like this, thank you.

tetromino_• 4 months ago

Attempting to access treedix.com (the advertised product) gives me

Access Denied
Sorry, you do not currently have the necessary permissions to access this site, or this site may not be available in your region.

Are they geoblocking the USA from even viewing their site for some reason?

LeoPanthera• 4 months ago

It's available on Amazon in the US.

rationalist• 4 months ago

Except that I can't even load the page to see the model name or whatever to see what specific device I should search for on Amazon. I guess I could just search the brand and wade through all the different listings.

dceddia• 4 months ago

I was connected to a VPN and saw the same. Went away once I disconnected.

(Must say I'm not a fan of how, increasingly, taking any steps to preserve privacy is seen as deviant, or justified because bots)

mxfh• 4 months ago

Like the price point and portability of the base Treedix testers.

Talking about near perfect wishlist:

Some standard hardware with fail-safe power connections a set of fully wired ports like in display-less Treedix USB platine tester version.

On the other side powered and extended diagnostics through USB-C can then be done from any smartphone or pc providing the display and updateable extended software layer.

Bonus for connectivity to some brother label printers.

throwpoaster• 4 months ago

The only downside of the USB cable tester is that I would love to support more plugs on the B side: USB-A (for my Frankencables) and USB B (which everyone but seems to think extinct).

Music production peripherals, until the recent USB C transition, commonly used USB B for some reason. Anyone know why?

marcosscriven• 4 months ago

I haven’t yet worked out why cheap 100W PD cables partially fail after about 6 months.

They can still provide some power, but between a MacBook and official Apple power supply, they’ll keep flicking between charging and not charging.

bennysaurus• 4 months ago

Likely the emarker chip in the cable is reporting higher power capabilities than the cable can support long term. It'll work initially but then can't maintain that after resistance in the wires increase with wear.

superxpro123• 4 months ago

My personal favorite is the usb-c cable that works when you rotate the connector upside-down.

A nearly perfect USB cable tester

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