# Notes: USB-C cables

Research date 2026-10-19. Scope: cables with at least one USB-C end (C-to-C, C-to-A, C-to-Lightning) bought for charging, data or video. The taxonomy leaf `cable` is broader (HDMI, Ethernet, audio, power cords); these notes cover USB-C only.

Quote labels: **verbatim** = text I read directly (PDF extracted locally with pdftotext). **fetched excerpt** = sentence returned by WebFetch's summariser as a quote; wording is the page's as far as the summariser is reliable. **search excerpt** = sentence surfaced in a search-result summary; weakest grade.

## Seed

seed.py gave: example = kitchen knives, steel hardness (a numeric spec that only makes sense as one side of a trade-off, with a community axis); persona = an allergist (exposure, dose, what is hidden in the ingredients list).

1. USB-C equivalent of steel hardness: **cable length against achievable data rate.** Length is the number every listing carries. For a passive cable it is one side of a trade-off: the longer the cable, the lower the top speed it can honestly carry (0.8 m for 40 Gbps, about 1 m for 10 Gbps, 2 m for 5 Gbps, 4 m for USB 2.0). The community draws this as tables; it is really a step chart with length on one axis and speed on the other. Kept: `cable_length` as a split, the `honest_speed_at_length` derived metric, and the two-axis visual grammar.
2. What an allergist would notice first: **what is hidden inside the overmold.** The e-marker chip, or its absence, decides whether a cable may carry more than 3 A. The 56 kΩ resistor inside a C-to-A cable stops the phone from drawing more current than the USB-A charger can give (the "dose" the source can deliver). Charge-only cables omit data wires and look identical from outside. Some 240 W cables add thermistors. Kept: `e_marker`, the "charge-only, no data wires" value of `data_rate`, `legacy_resistor_56k` for C-to-A, `certification` as the only label a buyer can check. Dropped: thermistors as a facet (one teardown, one brand) and wire gauge (not published; the teardowns I read do not report it either). Both are high_signal_markdown material.

## Sources

### usbif_cable_logo_guidelines (standards_body)
URL: https://www.usb.org/sites/default/files/usb_type-c_cable_logo_usage_guidelines_20240903.pdf
verbatim (pdftotext): "All USB-C® to USB-C cables are required to use the USB-IF approved cable logo on the cable in the form of either being embossed on the over mold or printed on the overmold". "all USB-C® to USB-C cables must be labeled using the appropriate data rate and power wattage cable logo. For example, a USB 20Gbps cable that supports 20V at 3A must be marked with the Combined Performance and Power 20Gbps/60W logo." "While USB 2.0 Type-C® 240W and 60W cables that delivers data at up to 480Mbps, this data performance capability is not required to be included on the cable and is not reflected in the charging logos." Also: "Logo Usage Guidelines for USB 80Gbps, 40Gbps, 20Gbps, 10Gbps and 5Gbps Performance Logos can be found here."
Supports: certified cables carry a combined power/data logo on the overmold; USB 2.0 cables carry only a wattage logo; the logo families are 60 W and 240 W by 5/10/20/40/80 Gbps. Confidence high.

### usbif_power_logo_press_2021 (standards_body)
URL: https://www.usb.org/sites/default/files/2021-09/USB-IF_Cable%20Power%20Rating%20USB4%20Logo%20Announcement_FINAL.pdf
verbatim (pdftotext): "Certified USB Type-C Cables will now feature logos highlighting support for 60W or 240W of power as defined by the recently published USB Power Delivery (USB PD) 3.1 Specification." Dated September 30, 2021. "USB-IF reminds consumers to purchase certified products from trusted sources that display USB-IF Certified Logos on packaging, product briefs, or the device, charger, and cable itself."
Supports: the two power classes on logos are 60 W and 240 W; USB-IF's own advice is to look for the logo. Confidence high.

### usbif_cable_connector_page (standards_body)
URL: https://www.usb.org/cable_connector
fetched excerpt: "all USB-C® to USB-C cables categories must be labelled with either a power capability of 60W or 240W by using the appropriate power icon and/or logo." "all cables except for High-Speed USB (USB 2.0) USB-C to USB-C cables, are required to be marked with the appropriate data rate they can support."
Supports: same as above, second source. Confidence high.

### gigazine_usbif_product_search (other)
URL: https://gigazine.net/gsc_news/en/20231202-usb-if-product-search
fetched excerpt: the USB-IF Product Search lets you filter by "MODEL/PART NUMBER" or company; when the author checked popular Amazon cables, most returned "No Products Found"; one ELECOM cable appeared as "certified in 2020".
Supports: certification can be verified against usb.org/products; most consumer cables are not in it. Confidence medium (single walkthrough, Dec 2023).

### grl_pd31_intro (primer)
URL: https://www.graniteriverlabs.com/en-us/technical-blog/usb-power-delivery-specification-3-1
fetched excerpt: EPR "was added to expand the maximum wattage of the PD 3.0 power supply from 100W to 240W (48V 5A)". "EPR cables must contain an E-Marker to clarify this capability. The E-Marker must be set to EPR Mode Capable and provide notification that it supports 50V and 5A." "The minimum working voltage of EPR cables must be at least 53.65V."
Supports: 240 W = 48 V × 5 A; 240 W cables need an EPR e-marker. Confidence high (GRL is a USB-IF test lab).

### wikipedia_usb_c (primer)
URL: https://en.wikipedia.org/wiki/USB-C
fetched excerpt: "Every USB‑C cable must support at least three amps of current and up to 20 volts". "All Type‑C cables except the minimal combination of USB 2.0 and only 3 A must contain E-marker chips". "USB 2.0 Type‑C cables do not include wires for SuperSpeed or sideband use." "Cable length should be 2.0 m or less for Gen 1 and 1.0 m or less for Gen 2". "Thunderbolt 3 (40 Gbit/s) Alternate Mode with cables longer than 0.8 m requires active Type‑C cables". "The combination of higher voltage support and 5 A current support is called Extended Power Range (EPR) and allows for up to 240 W".
Supports: 3 A floor; e-marker rule; USB 2.0 cables lack SuperSpeed wires; 2 m / 1 m / 0.8 m length ceilings; EPR definition. Confidence high.

### adafruit_cable_lengths (primer)
URL: https://learn.adafruit.com/understanding-usb-type-c-cable-types-pitfalls-and-more/cable-lengths
fetched excerpt: "the faster the speed of a USB cable, the shorter it should be". "USB 2.0 - Up to 5 meters." "USB 3.1 Gen 1 - Up to 3 meters." "USB 3.1 Gen 2 - Up to 0.8 meter." "USB4 - Up to 0.8 meter." "Copper Thunderbolt 4 cables up to 1 m (3.3 ft) are passive cables, while longer cables must integrate active signal conditioning circuitry."
Supports: length limits speed; 0.8 m for 40 Gbps. DISAGREES with Wikipedia/Plugable on Gen 1 (3 m vs 2 m), Gen 2 (0.8 m vs 1 m) and USB 2.0 (5 m vs 4 m). Confidence medium.

### plugable_active_passive (primer)
URL: https://plugable.com/blogs/news/what-s-the-difference-between-active-and-passive-thunderbolt-cables
fetched excerpt: passive Thunderbolt cables: "40Gbps if under 0.8m (2.6ft)" and "20Gbps if over 0.8m (2.6ft)"; active: "40Gbps up to 2m (6.6ft)". "you can get an active Thunderbolt 3 cable, but it only transmits Thunderbolt data–not USB."
Supports: 0.8 m passive line for 40 Gbps; active cables reach 2 m; active TB3 cables drop USB. Confidence high.

### plugable_decoding_2026 (primer)
URL: https://plugable.com/blogs/news/decoding-usb-standards-2026
fetched excerpt: "USB 3.2 Gen 1x1 = 5Gbps; USB 3.2 Gen 2x1 = 10Gbps; USB 3.2 Gen 2x2 = 20Gbps"; USB4 "USB 40/80Gbps"; passive guidance "up to 2m/6.6ft for 5Gbps; up to 1m/3.3ft for 10/20Gbps"; "Passive USB4 40Gbps cables are commonly limited to 0.8m/2.6ft."
Supports: data-rate naming map; passive length ceilings. Confidence high.

### plugable_kb_cables (primer)
URL: https://kb.plugable.com/usb-c-cables/usb-type-c-cable-compatibility-length-and-features
fetched excerpt: "USB Type-C charging cables support only USB 2.0 data and USB-C Power Delivery" and "lack USB 3 and video capability." "USB Type-C data cables can support data rates at or above 5Gbps with four dedicated data paths for USB 3 data or USB-C DisplayPort Alternate Mode video." Table: USB 2.0 up to 4 m, USB 3.2 Gen 1 up to 2 m, Gen 2 up to 1 m, USB4 up to 0.8 m, Thunderbolt 3 up to 1 m, Thunderbolt 4 up to 2 m. "Passive USB4 and Thunderbolt 4 cables are backwards compatible with previous generation USB Type-C hosts and devices".
Supports: USB 2.0 cables cannot carry DisplayPort video; full-featured cables can; the 4/2/1/0.8 m ladder. Confidence high.

### asmr_usb4_length (primer)
URL: https://asmr.education/faq/usb-c/usb4-cable-max-length-passive-active
fetched excerpt: "The maximum length for a passive USB4 cable operating at the full 40 Gbps (Gen 3) data rate is 0.8 meters". "Passive cables up to 2 meters can still carry USB4 traffic, but only at the reduced Gen 2 speed of 20 Gbps." "a 1.2 meter passive cable that cannot sustain Gen 3 signaling may silently fall back to Gen 2 or even USB 3.2 speeds".
Supports: 0.8 m / 2 m USB4 tiers; silent fallback. Confidence medium (secondary explainer).

### chromium_cable_tips (other)
URL: https://www.chromium.org/chromium-os/developer-library/reference/hardware/cable-and-adapter-tips-and-tricks/
fetched excerpt: "No. You must use the 56 kΩ Rp. The resistor indicates the capability of the power adapter, not the capability of the cable." "It is not safe to use the 3A Rp: if the power adapter is not capable of providing 3A it could overheat." "All cables must be capable of supporting 3A, regardless of Rp/Rd".
Supports: 56 kΩ rule for C-to-A; 3 A floor; what the resistor signals. Confidence high (Google ChromeOS hardware reference).

### laptopmag_safe_cables (specialist_review)
URL: https://www.laptopmag.com/articles/how-to-find-safe-usb-type-c-cables
fetched excerpt: "With a 56K Ohm resistor and the right components on board, a standards-compliant cable will make sure that the client tries to draw only as much electricity as the host can provide." "A poor-quality wire, however, fools the phone into thinking that it's connected to a 3-amp-capable power source. When the phone tries to draw 3 amps, it can cause permanent damage." Leung "fried both the USB ports (and the host controller) on his Pixel C laptop." "buying one that is certified by the USB-IF is a good start."
Supports: 56 kΩ mechanism and consequence; certification as the buyer's check. Confidence high.

### pcworld_43_cables (specialist_review)
URL: https://www.pcworld.com/article/1063892/we-tested-43-old-usb-c-to-usb-a-cables-1-was-great-10-were-dangerous.html
fetched excerpt: "We tested 43 old USB-C to USB-A cables." "The remaining 10 cables were constructed improperly." "Five were built incorrectly with either a 22k ohm resistor, or incorrect wires with the 56k ohm resistors. The remaining five had no 56k ohm resistors at all." Tool: "ADUSBCIM Cable Checker 2".
Supports: C-to-A resistor defects are common enough to matter (10 of 43). Confidence high.

### pcworld_best_cables (specialist_review)
URL: https://www.pcworld.com/article/395115/the-best-usb-c-cables-for-charging-and-transferring-data.html
fetched excerpt: tools "USB Cable Checker 2.0", "milli-ohm meter", thermal imaging under load. "All but one of the cables met those claims, but the one that was wrong was way, way wrong." (falsely advertised USB 3.2 10 Gbps and wrong length). "To hit 40Gbps, you'd have to step down to a shorter cable." Basic USB 2.0 cables 480 Mbps vs full-featured 10/40 Gbps plus video.
Supports: reviewers verify by reading the e-marker and wiring; mislabelled cables exist; shorter for 40 Gbps. Confidence high.

### pcworld_cable_audit (specialist_review)
URL: https://www.pcworld.com/article/3175338/i-audited-my-usb-cables-with-this-50-tester-and-was-surprised-how-bad-some-of-them-are.html
fetched excerpt: one cable "has no data transmission capabilities at all—only basic power transmission"; a cable "with a USB 3.1 Gen 1 label on it" tested as "rated for up to USB4 data speeds and 100W charging".
Supports: labels and insides diverge both ways; charge-only cables exist in the wild. Confidence medium (anecdotal audit).

### pcworld_magnetic (specialist_review)
URL: https://www.pcworld.com/article/2307079/dont-buy-these-dangerous-usb-c-accessories.html
fetched excerpt: risks listed: "The risk of static electricity discharge." "Data loss and performance degradation from electronic magnetic interference from the exposed POGO pins." "The risk of electrical arc damage across the pins in high-humidity environments." "The potential for debris to short out the exposed magnetic pins." Magnetic adapters "are not officially part of the USB-C specification".
Supports: magnetic tips are a safety exclusion. Confidence high.

### howtogeek_magnetic (primer)
URL: https://www.howtogeek.com/stop-using-magnetic-usb-c-cables-they-can-kill-your-device/
fetched excerpt: "if, even for a fraction of a second, the pins that aren't meant to touch bridge, they can create a massive voltage spike that fries your device's internals." Magnets "can attract tiny metallic debris and even larger items like staples and needles, which can bridge the connection between two pins".
Supports: same, second source. Confidence high.

### techgearlab_cables (specialist_review)
URL: https://www.techgearlab.com/topics/electronics/best-usb-c-cable
fetched excerpt: "measured their charging rate using USB multimeters, tested their ability to display video, and transferred large files". Durability: "bending each cable over 100 times". A budget cable "frequently carried 3-5% less wattage than the more premium competition". Copying a 20 GB file: under 30 s on 40 Gbps vs over 9 min on 480 Mbps.
Supports: the practical size of the USB 2.0 vs 40 Gbps gap; reviewers test video separately. Confidence high.

### chargerlab_apple_240w (specialist_review)
URL: https://www.chargerlab.com/teardown-of-apple-240w-usb-c-charge-cable-a2794
fetched excerpt: "an E-marker chip manufactured by Infineon, specifically the CYPD2803 model"; "its data transfer is limited to USB 2"; "The cable length is exactly 2m (6' 6.72'')"; diameter "about 4.6mm (0.18 inches)"; weight "about 78g (2.75 oz)". Three red positive wires and four bare negative wires in parallel; gauge not stated.
Supports: a flagship 240 W cable is USB 2.0 data; 240 W cables are thick and heavy; teardowns do not publish AWG. Confidence high.

### chargerlab_belkin_240w (specialist_review)
URL: https://www.chargerlab.com/teardown-of-belkin-240w-dual-usb-c-braided-cable
fetched excerpt: "Both ends are equipped with E-Marker chips and thermistors to ensure that over-temperature protection can be triggered from either end." E-marker "WCH, model CH254X". Five cores: positive, negative, D+, D-, CC. "Its data transfer capability is USB 2.0".
Supports: 240 W cables are typically USB 2.0; some add thermistors (one brand, one source, so not a facet). Confidence high for this cable, low for generalising.

### chargerlab_baseus_240w (specialist_review)
URL: https://www.chargerlab.com/new-rating-logo-teardown-of-baseus-240w-usb-c-cable/
fetched excerpt: e-marker "Hynetek HUSB332B". search excerpt (same article): "The first chip to get USB PD3.1 eMarker certification, supporting PD3.1 EPR 240W power transmission and USB4 Gen3 40Gbps"; cable about 1 m, diameter about 3.38 mm; title says the cable carries the "New Rating Logo".
Supports: the USB-IF rating logo appears on real cables; 1 m 240 W/40 Gbps cables exist. Confidence medium.

### anker_240w_cable_page (spec_sheet)
URL: https://www.anker.com/products/a82e2-240w-usb-c-to-usb-c-cable
fetched excerpt: spec table headings "MAX Output", "Cable Type", "Cable Length", "Compatibility", "Bend Lifespan", "Specification Met". Values: "240W", "480 Mbps", "USB-IF", bend lifespan "over 30,000", lengths 3 ft / 6 ft / 10 ft, "does not support screen mirroring".
Supports: what a leading brand publishes; a 240 W cable at USB 2.0 cannot drive a monitor; bend-count as a brand claim. Confidence high.

### anker_data_cables_blog (primer)
URL: https://www.anker.com/blogs/cables/are-all-usb-c-cables-data-cables
fetched excerpt: "USB-C charging cables usually have two wires inside: one for positive power (V+) and one for ground (V-)." USB 2.0 Type-C "up to 480 Mbps"; USB 3.0 "up to 5 Gbps"; USB 3.1 Gen 2 "up to 10 Gbps"; Thunderbolt 3 / USB4 "up to 40 Gbps".
Supports: charge-only cables exist; speed ladder. Confidence medium (vendor explainer).

### anker_a_to_c_faq (spec_sheet)
URL: https://service.anker.com/article-description/Anker-USB-A-to-USB-C-Cable-FAQ
fetched excerpt: "Yes. The purpose of the 56K ohm resistor is to determine the power transfer mode." Charging: "Quick Charge 18W fast charging when paired with a Quick Charge charger" and "5V/2A" with standard chargers.
Supports: C-to-A cables top out around 18 W; the 56 kΩ resistor is a stated spec. Confidence high for Anker's cables.

### belkin_240w_cable_page (spec_sheet)
URL: https://www.belkin.com/p/usb-c-to-usb-c-braided-cable-240w-3.3ft%2F1m-white/CAB025fq1MWH.html
fetched excerpt: Wattage 240W; Jacket "Braided PCR"; lengths 1 m / 2 m / 3 m; "350,000+ bends"; "20,000+ plug-ins"; 2-year warranty. No data-rate field shown. CORRECTION after the blind check (re-fetched 2026-10-19): the page says "Certified by Intertek TE-00114861" and GRS certifications by Intertek; the string "USB-IF" does not appear. The first fetch's "USB-IF certified" was a summariser error.
Supports: brand spec fields; bend counts vary by orders of magnitude between brands (350,000 vs Anker's 30,000) so they are not comparable; wattage-only listings omit data rate. Confidence high.

### belkin_a_to_c_15w_page (spec_sheet)
URL: https://www.belkin.com/p/usb-a-to-usb-c-cable-15w/CAB010bt1MBK.html
fetched excerpt: Wattage "15W"; Data Rate "USB 2.0 (480 Mbps)"; "30,000+ bends"; "Double-braided nylon with silicone".
Supports: a C-to-A cable is sold as a 15 W cable. Confidence high.

### bgr_a_to_c (primer)
URL: https://www.bgr.com/2258027/can-usb-a-to-c-cable-fast-charge-device/
fetched excerpt: USB-A ports "max out at around 2.5 watts for USB 2.0 and 15W for USB 3.0".
Supports: the USB-A end caps power well below PD levels. Confidence medium.

### plugable_tb5_cable (spec_sheet)
URL: https://plugable.com/products/tbt5-240w1m
fetched excerpt: "80Gbps Bi-Directional; Up to 120Gbps with Bandwidth Boost"; "1m (3.3ft)"; passive; "Up to 240W"; "Thunderbolt and USB-IF Certified, third party tested to UL 9990 standard"; "backward compatible with Thunderbolt 4, Thunderbolt 3, USB4, and USB-C".
Supports: 80 Gbps passive cables are sold at 1 m; such cables carry both certifications. Confidence high.

### tbt_tb5_passive_cable (spec_sheet)
URL: https://www.thunderbolttechnology.net/product/thunderbolt-5-80120gbps-08m%EF%BC%8F1m-passive-epr240w-cable
fetched excerpt: "Thunderbolt 5 will deliver 80Gbps of bi-directional bandwidth, and with Bandwidth Boost it will provide up to 120Gbps"; "Length： 0.8 meter / 1 meter"; "Maximum power delivery capacity up to 48V/5A（240W）".
Supports: passive 80 Gbps tops out at about 1 m. Confidence high (Intel's Thunderbolt product listing).

### apple_mfi_counterfeit (other)
URL: https://support.apple.com/en-us/111103
fetched excerpt: "Apple recommends using only accessories that Apple has certified and that come with the MFi badge." Counterfeits: "Your iOS device could become damaged", "The connector end might fall off, get very hot, or might not fit properly." Genuine Apple cables read "Designed by Apple in California" about seven inches from the USB end with "a 12-digit serial number".
Supports: for C-to-Lightning, MFi is the certification that matters. Confidence high.

### wikipedia_mfi (primer)
URL: https://en.wikipedia.org/wiki/MFi_Program
fetched excerpt: "Apple Inc.'s MFi Program, short for 'Made for iPhone/iPod/iPad', is a licensing program for developers of hardware and software peripherals". "The Lightning connector, introduced in 2012, added additional protocols that could only be certified through the MFi Program."
Supports: definition of MFi. Confidence high.

### usbconnectioninfo_emarker (primer)
URL: https://usbconnectioninformation.com/guides/usb-c-cable-emarker-chips/
fetched excerpt: the e-marker publishes "Maximum current - 3A or 5A", "Maximum voltage - 20V, or up to 50V for Extended Power Range (EPR)", "Maximum data rate - USB 2.0 / 5 Gbps / 10 Gbps / 20 Gbps / 80 Gbps", "Passive or active construction", "Vendor ID of the chip." Required if "rated for high speed (above USB 2.0) or high power (above 60W / 3A)." "Windows does not expose USB-C cable e-marker data to applications".
Supports: what the e-marker declares; when it is required; it can be read on macOS, not Windows. Confidence medium (hobbyist site, consistent with Wikipedia and GRL).

### treedix_tester (spec_sheet)
URL: https://treedix.com/products/treedix-usb-cable-tester-usb-c-cable-tester-usb-tester-for-data-transmission-and-power-transmission-cable-testing-resistor-testing-type-c-emarker-for-usb-a-micro-b-micro-b-3-0-type-c-lighting-mini-b
search excerpt: reads "eMarker chip parameters in Type-C cables ... maximum current, voltage, and data transfer rates"; identifies "USB 2.0 and USB 3.2" wiring; "PD 3.0 and PD 3.1 protocol detection".
Supports: consumer testers exist that read the e-marker, so a backfill-by-testing path is realistic for the top of the catalog. Confidence medium.

### makeuseof_three_numbers (primer)
URL: https://www.makeuseof.com/i-learned-three-usb-c-numbers-specs-actually-mean/
fetched excerpt: "Data transfer speed is arguably the most important spec to consider when purchasing a USB-C cable." "high-speed data cables might not support fast charging speeds, and vice versa."
Supports: power and data are independent ratings on a cable. Confidence medium.

### target_search_240w (retail_listing)
URL: https://www.target.com/s?searchTerm=usb+c+cable+240w
fetched excerpt: result cards show "Apple 240W USB-C Charge Cable (2m)", "Heyday 6' USB-C to USB-C 240W Fast Charging Braided Cable", "Beats 240W USB-C to USB-C Braided Cables (3m)" with only wattage, length and jacket in the title; no data rate.
Supports: mass-market listings carry wattage, length and jacket; data rate is usually absent. Confidence medium. Note: Amazon, Walmart, Best Buy, Micro Center, Newegg, Adorama and B&H all blocked fetches today, so the retail survey rests on Target plus three brand pages and the Amazon titles seen in search results ("Cable Matters [Intel Certified] 40Gbps Active Thunderbolt 4 Cable, 6.6ft").

### alibaba_jacket_durability (other)
URL: https://seller.alibaba.com/blogs/2026/southeast-asia/electronics-accessories/usb-cable-material-durability-comparison-alibaba-b2b-guide
search excerpt: "Nylon braided cables deliver 10,000-20,000+ bend cycles ... TPE cables ... 5,000-7,000 bend cycles ... silicone ... 8,000+ bend cycles". Silicone "is prone to cuts/tears".
Supports: rough ordering of jacket durability. Confidence low (manufacturer-side marketing guide, no method stated).

## Disagreements kept side by side

| Claim | Side A | Side B | Call |
|---|---|---|---|
| Max passive length at 5 Gbps | 2 m (wikipedia_usb_c, plugable_decoding_2026, plugable_kb_cables) | 3 m (adafruit_cable_lengths) | 2 m. Three sources, including the spec summary. |
| Max passive length at 10 Gbps | 1 m (wikipedia, plugable x2) | 0.8 m (adafruit) | 1 m. Same reasoning. |
| Max USB 2.0 Type-C length | 4 m (plugable_kb_cables; Infineon KB via search excerpt) | 5 m (adafruit; generic USB 2.0 figure) | 4 m. The Type-C spec figure, not the old USB 2.0 figure. |
| Passive 20 Gbps length | 1 m (plugable_decoding for USB 3.2 2x2) | 2 m (asmr_usb4_length for USB4 Gen 2) | Both true for different protocols. Use 1 m as the safe line in the derived metric; note 2 m for USB4 Gen 2. |
| Passive Thunderbolt 4 at 40 Gbps | 0.8 m (plugable_active_passive, wikipedia for TB3) | 1 m (adafruit) | up to 2 m (plugable_kb_cables table; retail titles for 2 m "active" TB4 cables) | 0.8 m is the only line all sources accept for passive 40 Gbps; TB4 cables sold at 2 m are active or specially qualified. |
| Bend-cycle counts | Anker "over 30,000" | Belkin "350,000+" (same 240 W class) | Not comparable across brands; show as an annotation, never sort on it. |

## Listing field survey (what is present today)

- Brand pages: Anker publishes MAX Output, Cable Type, Cable Length, Compatibility, Bend Lifespan, Specification Met (USB-IF). Belkin publishes Wattage, Jacket Material, Length, Bend Test, Plug-in count, Certifications, Warranty, and omits data rate on its 240 W cable. Plugable publishes data rate, Bandwidth Boost, length, passive/active, wattage, certifications, display support.
- Mass-market titles (Target, Amazon titles via search): wattage, length, jacket ("braided", "silicone"), sometimes "Active", sometimes "[Intel Certified]"; data rate only on cables sold for data.
- Absent almost everywhere: e-marker (sometimes a bullet), 56 kΩ resistor (sometimes in the title for C-to-A), USB-IF TID, wire gauge, passive vs active unless active is a selling point.
- Existing add-on fields (`cable.jsonc`): cable_type, connector_a_raw, connector_b_raw, spec_version_raw, power_delivery_watts, ethernet_category, sizing.length_ft, sizing.gauge_awg.

## Against the existing add-on schema

Proposals only. Classification uses AGENTS.md's four allowed kinds; everything else is high_signal_markdown material.

| Doc facet | In add-on today? | Proposed kind | Note |
|---|---|---|---|
| connector_ends | yes, as connector_a_raw / connector_b_raw (free text) | hard filter | Worth an enum: usb_c, usb_a, lightning, micro_usb, hdmi, displayport, audio_3_5mm, other. Raw strings cannot be filtered on. |
| data_rate | partly, as spec_version_raw (free text) | quality currency | Normalise to an ordinal in Gbps (0.48, 5, 10, 20, 40, 80) with a charge_only value. This is the number the category is compared on, and it must be dense; default C-to-C wattage-only listings to 0.48. |
| power_rating | yes, power_delivery_watts | quality currency | Keep. Add the class mapping (60 / 100 / 240) at read time, not as a field. |
| cable_length | yes, sizing.length_ft | sizing | Keep. Store metres or feet consistently; the speed ceilings are in metres. |
| active_or_passive | no | hard filter (small) or markdown | Only matters above 1 m at 40 Gbps+. Could be a boolean `active`. Low fill; fine as markdown. |
| e_marker | no | derived at read time | Required by spec above 3 A or above USB 2.0, so derive from power and data rate; a listing bullet saying "E-Marker" is confirmation only. Not a field. |
| certification | no | hard filter | Enum: usb_if, thunderbolt, mfi, none_claimed. The verified-in-registry flag is a researched backfill (usb.org/products), top N only. |
| video_capable | no | derived | data_rate >= 5 Gbps. Not a field. |
| jacket_material | no | image pipeline | Braided vs smooth is visible in the photo (rule 1). Silicone vs TPE is not visible; markdown. |
| bend_cycle_rating | no | markdown | Brand claims, incomparable. Never a field. |
| magnetic_tip | no | hard filter (exclude) | Boolean from the title. Cheap and protective. |
| legacy_resistor_56k | no | markdown | C-to-A only; appears in titles when present. |

Add-on fields the doc considers noise for USB-C: `sizing.gauge_awg` (almost never stated; the e-marker rating supersedes it; keep for speaker wire and power cords), `ethernet_category` (not applicable here; fine for the broader leaf). `cable_type` is useful at the leaf level to separate USB-C from HDMI and Ethernet, but its usb_charging / usb_data split duplicates data_rate.

## Additions after the STYLE pass

- wikipedia_usb_c, search excerpt: "USB-C is a 24-pin reversible connector". Supports the 24-pin count in the mechanism. Confidence high.
- pcworld_best_cables, search excerpt (from the how-we-test article the search summarised): "A 'full featured' USB-C cable can have up to 18 wires inside and 24-pins in the plug". Supports "up to 18 wires". Confidence medium.
- Tester cost: pcworld_cable_audit title names "this $50 tester"; pcworld_43_cables names the "$65 ADUSBCIM Cable Checker 2". Supports "a tester costing under 100 dollars". Confidence high.
- Shortest passive cables: adafruit_cable_lengths lists Thunderbolt 5 passive cables at "1 foot, 1.6 feet and 3.3 feet" (0.3 to 1 m); tbt_tb5_passive_cable lists 0.8 m and 1 m. Supports the 0.3 m floor and the 0.3 to 1 m cluster. Confidence medium.
- 3 m cables are charging cables: belkin_240w_cable_page offers 3 m on a USB 2.0 240 W cable; target_search_240w shows "Beats 240W USB-C to USB-C Braided Cables (3m)". Confidence medium.
- EPR fallback: search excerpt (digi-electronics e-marker guide, not fetched): "without the EPR E-Marker, a 240W charger silently falls back to 100W". Used only to phrase the softer claim that a charger will not offer more than the cable's e-marker declares, which follows from grl_pd31_intro and usbconnectioninfo_emarker. Confidence medium.
- Dropped claim: "a Mac reports the e-marker in its system information". The source (usbconnectioninfo_emarker) describes its own menu-bar app, not Apple's System Information, so the claim was not supported. Replaced with the Windows statement the source does make.

## Blind-check corrections (2026-10-19)

1. USB-A ceiling. The doc said a USB-A end "cannot exceed about 18 W whatever the listing says". Reworded to the USB-rules ceiling (about 15 W, 18 W with Quick Charge) with the proprietary exception stated. New sources: wikipedia_vooc (primer, fetched excerpt: "VOOC cable, comes in three variants, 6.5 amp 10 volt, 10 amp 10 volt and 13.7 amp 11 volt"; the 240 W version "requires the use of bundled proprietary charger and proprietary USB-C cable") and flipkart_oppo_dl129 (retail listing, search excerpt from the title: "OPPO USB Type C Cable 8 A 1 m 80W ... up to 80W Max*(11V/7.3A) DL129 ... USB-A TO USB-C"). Confidence medium: one primer and one listing title; an OPPO support page was not reachable.
2. Wire count. Mechanism now says five wires always exist (power, ground, CC, D+, D-), matching chargerlab_belkin_240w's five cores. "Up to 18 wires" dropped everywhere; it came from a search excerpt of a PCWorld page I could not fetch, so it is not cited.
3. EPR fallback. "A non-EPR cable caps a 240 W charger at 100 W" removed. The Renesas application note (fetched, pdftotext) and Belkin's Power Delivery explainer (fetched) do not state it in words I could quote; the only statement found was a search excerpt (digi-electronics). Replaced with what grl_pd31_intro and usbconnectioninfo_emarker do say: a 240 W cable's e-marker must declare 50 V and 5 A, and that declaration is how the charger learns it may exceed 20 V.
4. cable_length.range.min 0.3 m now cites adafruit_cable_lengths in the facet's evidence.
5. bend_cycle_rating. Numeric min/max dropped. "typical" now rests on belkin_flex_cable_page (fetched excerpt: "Withstands up to 25,000 bends based on internal laboratory test result, compared with 1,000 bends for an ordinary PVC cable"), belkin_240w_cable_page (350,000+) and anker_240w_cable_page (over 30,000). The checker's Anker 333 / Amazon Basics 5,000 figures were not fetched by me, so they are not cited.
6. Belkin 240 W certification corrected (see the source entry above). No JSON claim depended on Belkin being USB-IF certified; the reference's supports line now says Intertek, no USB-IF claim.
7. Sources reclassified: data_rate -> derived (parsed when stated, defaulted by rule otherwise); active_or_passive -> derived; legacy_resistor_56k -> researched, backfill medium. bend_cycle_rating stays listing, with the justification in its backfill_note (only brands that test publish it, in a spec field; absence means not stated).
8. Splits 3 and 4 reworded to cable-specific questions: "Will this cable ever carry laptop power, or only phone and earbud power?" and "How long a cable: under a metre for a desk, about two metres for a bedside, or longer?" The metre thresholds in the second are the speed steps, which an extension cord does not have.

## Branches (2026-10-19)

Each branch is keyed on the split facet's own values (or, for `cable_length`, the answer labels the question offers) and follows from a sentence already in the register or these notes.

- `connector_ends` = USB-C to USB-C: skip `legacy_resistor_56k`. From the facet definition: "For USB-C to USB-A cables only, whether the cable contains the 56 kΩ resistor."
- `connector_ends` = USB-C to USB-A: ask `legacy_resistor_56k`; skip `power_rating`, `video_capable`. From the split rationale: "A USB-A end stays at about 15 to 18 W under the USB rules and never carries video", and `connector_ends.why_experts_care`: "A C-to-A cable also needs a 56 kΩ resistor inside."
- `connector_ends` = USB-C to Lightning: ask `certification`; skip `power_rating`, `legacy_resistor_56k`. From the split rationale: "a Lightning end brings its own certification"; mechanism family "USB-C to USB-A or Lightning cable": "One end is the older connector, which caps power at about 15 to 18 W"; and the resistor definition above.
- `connector_ends` = USB-C to other: no branch. The register says nothing specific about HDMI, DisplayPort, micro-USB or 3.5 mm ends.
- `data_rate` = charge-only or USB 2.0: skip `video_capable`, `active_or_passive`. From `video_capable.why_experts_care`: "A USB 2.0 cable has no high-speed wires, so it cannot drive a monitor", and `active_or_passive.why_experts_care`: "This only matters above about 1 m at 40 Gbps or more." The files-or-monitor answer continues the normal sequence, so it has no branch; the active-or-passive question is raised by the length split.
- `power_rating` = up to 60 W: skip `e_marker`. From `power_rating.why_experts_care`: "Every USB-C cable must carry 3 A ... Above that the cable needs an e-marker", and the value label "no e-marker needed".
- `power_rating` = 100 W or 240 W: show `e_marker`. From `e_marker.why_experts_care`: "Without an e-marker a charger will not send more than 3 A whatever the listing claims."
- `cable_length` = under a metre: skip `active_or_passive`. From the split rationale: "under 1 m any speed is available", and `active_or_passive.why_experts_care`: "This only matters above about 1 m at 40 Gbps or more."
- `cable_length` = about two metres: ask `active_or_passive`. From the split rationale: "over 1 m, 40 Gbps needs an active cable", and `active_or_passive.why_experts_care`: "Passive 40 Gbps cables top out at 0.8 m; active ones reach 2 m."
- `cable_length` = longer: skip `active_or_passive`, `video_capable`. From the split rationale: "over 2 m only USB 2.0 is within specification", and the USB 2.0 sentence under `video_capable` above.

## Trimmed detail (2026-10-19)

Sentences cut from capped fields. Numbers, names and claims are unchanged in the JSON; what follows is the detail that no longer fits.

- `summary`: "This document covers USB-C cables only, not the HDMI, Ethernet and audio cables that share the same catalog leaf." (Scope statement; also at the top of these notes.) The gloss "USB-IF, the USB standards body" was dropped; the vocabulary entry for USB-IF certified carries it.
- `mechanism.plain`: "a 24-pin plug that looks the same on every cable" lost "that looks the same on every cable"; the closing sentence "Nothing on the outside shows which wires or chips are inside" carries the point. "a chip in the plug that tells the charger the cable's current, voltage and speed limits" became "that declares its current, voltage and speed limits".
- `splits[0].rationale` (connector_ends): "only OPPO's proprietary SuperVOOC cables go higher, and only with their own charger and phone." The exception survives in shorter form in `connector_ends.why_experts_care` and in the wikipedia_vooc and flipkart_oppo_dl129 references. "before anything else is asked" became "first".
- `splits[3].rationale` (cable_length): "within the specification" became "within specification". Nothing cut.
- `connector_ends.why_experts_care`: "Qualcomm's Quick Charge" became "Quick Charge". "never the USB Power Delivery negotiation that lets USB-C go higher" became "never USB Power Delivery". "The one exception is OPPO's and OnePlus's SuperVOOC, a proprietary scheme whose own USB-A to USB-C cables are rated 6.5 A and up for 65 W to 80 W and work only with its own charger and phone" became "only OPPO's proprietary SuperVOOC cables go higher, with their own charger and phone" (the 6.5 A, 65 W to 80 W and OnePlus details sit in wikipedia_vooc and flipkart_oppo_dl129). "so the phone does not draw more than the charger can give" (the resistor's purpose) is stated in `legacy_resistor_56k.why_experts_care`. "'Made for iPhone' (MFi)" became "MFi"; the vocabulary entry expands it.
- `data_rate.why_experts_care`: wording only ("This is the rating that separates" to "This rating separates", "at all" dropped, "a high wattage" to "wattage"). Nothing cut.
- `power_rating.why_experts_care`: "under the Extended Power Range rules, the part of USB Power Delivery that allows the higher voltage" lost the gloss; the vocabulary entry for EPR carries it. "Power and data are set independently, so a 240 W cable is usually USB 2.0." cut; the summary, `data_rate.why_experts_care` (Apple's, Anker's and Belkin's 240 W cables are USB 2.0) and judgement 3 state it.
- `e_marker.why_experts_care`: wording only ("The chip is what reviewers read to check listings" to "Reviewers read the chip to check listings"; "means the cable is out of specification" to "means it is out of specification"). Nothing cut.
- `certification.why_experts_care`: "the overmold, the moulded plastic around the plug" lost the gloss; the vocabulary entry for Overmold carries it. "which says something about the market and nothing against any one cable" became "which says nothing against any one cable".
- `judgements[0].claim`: "sold longer than that at 40 Gbps" became "sold longer at 40 Gbps". Nothing cut.
- `references.plugable_decoding_2026.supports[0]`: the repeated "is" dropped. Nothing cut.
- `references.plugable_kb_cables.supports[2]`: "Length table:" became "Lengths:". Nothing cut.
- `references.belkin_240w_cable_page.supports[0]`: "with no USB-IF claim on the page" became "; no USB-IF claim". Nothing cut.
- `references.usbconnectioninfo_emarker.supports[0]`: original wording "The e-marker declares max current (3 or 5 A), max voltage (20 or 50 V), max data rate, passive or active, and vendor"; the repeated "max" is dropped, and the source entry above keeps the full quote (all three are maxima).

## Corrections log

### 2026-10-19, second pass: branches, questions, caps

- Branches added: 9, on all four splits (3 on connector_ends, 1 on data_rate, 2 on power_rating, 3 on cable_length). See "Branches (2026-10-19)" above.
- Questions rewritten: 6 distinct texts across 10 fields (4 split questions, each mirrored into its facet's cold_start_question, plus video_capable and jacket_material). All at most 12 words, no preamble, answers offered inline.
- Fields trimmed to cap: 14 (summary, mechanism.plain, 2 split rationales, 5 why_experts_care, 1 judgement claim, 4 reference supports lines). Cut detail recorded under "Trimmed detail (2026-10-19)".
- Unchanged: generated_at, facet/judgement/reference sets, evidence ids, priority scores.
- Validator clean; category.md and viewer.html regenerated.