Power markings answer one question
USB-IF’s current certified C-to-C cable power logos use 60 W or 240 W. More than 60 W requires a 5 A electronically marked cable. A legacy 100 W / 5 A claim can still describe an older compliant product, but it is not the current certified new-cable power logo.
Data labels should say the rate
Prefer explicit performance language—USB 5Gbps, 10Gbps, 20Gbps, 40Gbps, or 80Gbps—over generation names. USB 2.0 charge-first cables remain common and may be sufficient for charging while being unsuitable for fast storage or a full-featured display path.
| Claim | What it establishes | What it does not establish |
|---|---|---|
| 240 W | Power class, when genuine and applicable | High-speed data or video |
| USB 20Gbps | Declared USB data rate | 5 A charging or DisplayPort mode |
| USB4 40Gbps | Declared USB4 link class | Exact host display count or dock behavior |
| Thunderbolt | Certified ecosystem capability for the marked generation | Every monitor mode on every host |
Identify a cable without its packaging
- Inspect both connector housings and the cable jacket for watts, data rate, brand, and model. A color, thickness, or connector shape is not a capability record.
- Match the exact model and length to the manufacturer specification. If it claims USB-IF certification, check the USB-IF product search; a look-alike logo alone is not a verified record.
- Separate what is known: power rating, USB data class, and the intended display or USB4/Thunderbolt path. Do not fill an absent rating with a guessed wattage.
- Enter only those declarations in the Cable Capability Decoder. Leave power as Not stated / unknown if no rating is available; the result is a verification checklist, not a hardware test.
What an e-marker or tester can establish
A capable cable reader can retrieve advertised electronic identity fields, such as current capability, cable type, and supported signaling. That is different from testing the cable’s signal quality. USB-IF and Thunderbolt certification include electrical and interoperability checks in addition to identity data.
| Evidence | Useful conclusion | Still unknown |
|---|---|---|
| E-marker reading | The fields that this reader actually reports | Physical condition, certified compliance, or success on every host |
| Power meter | Power observed during that charging session | The cable’s maximum rating; charger, device and charge state also affect the reading |
| Transfer or display test | The tested mode works on that exact path | Untested higher rates, other modes, or which component limits a failed test |
Failure to obtain a marker reading is not proof of a particular power or data class. Check the reader’s capabilities and setup. This website cannot query an e-marker, inspect the wiring, or detect a connected cable.
Video is a path, not a cable sticker
A full-featured cable can carry DisplayPort Alt Mode only when the source port emits video and the sink or adapter accepts the intended mode. Purpose-built USB-C-to-DisplayPort or USB-C-to-HDMI cables are directional adapters, not general C-to-C data cables.
Active versus passive USB-C cables
Passive and active describe the signal path, not a quality score. A passive electronically marked cable can contain an identification chip without conditioning the data signals. Active cables use signal-conditioning electronics, such as a redriver, to support their documented link and length. An e-marker alone therefore does not make a cable active.
| Product | What changes | What to verify |
|---|---|---|
| Passive C-to-C cable | No active conditioning of the data signal; electronic identity may still be present | Exact rate, power class, supported mode and length |
| Active C-to-C cable | Electronics condition the supported signal | Supported USB/USB4/Thunderbolt/video modes, power and any HOST/SINK direction labels |
| Active video adapter | A converter changes the source protocol for the display input | Conversion direction and exact video/audio features, not only the word active |
At the same documented link class, “active” does not promise a faster application transfer. It also does not promise that every older protocol, display mode or charging power is supported. Do not infer construction or compatibility from cable length alone.
A reversible plug can still be on a directional cable
USB-C plug orientation and cable-end direction are different. For example, Cable Matters model 201034 explicitly labels HOST and SINK and requires a particular end at the computer. This is an exact-product example, not a claim that every active cable is directional. Follow the manual rather than swapping ends as a universal fix.
Choose by the intended job
- Write down the required USB data rate, USB4/Thunderbolt or display mode, power and cable length.
- Check those declarations for the exact cable, including direction and supported fallback modes.
- If the product converts USB-C/DisplayPort to HDMI, use the Video Adapter Direction Checker instead of treating it as a general C-to-C cable.
- Use the Cable Capability Decoder for documented power and data claims. Keep a missing claim unknown even when the other field is confirmed.
Length requires exact-model evidence
Signal integrity depends on rate, construction, certification, active electronics, and exact length. That is why Cable Check Lab does not offer a universal cable-length calculator: public standards do not turn one length number into a safe compatibility verdict.
Choose a controlled next test
Use a known-capable host and endpoint with one direct cable. Keep the port, device and workload unchanged when swapping cables. A low result is evidence about the whole path, not proof of a bad cable. Use the Data Path Checker for declared rate bottlenecks or Charge Check for charging requirements. Do not push an unverified cable to a higher load to discover its rating; stop using damaged or overheating components.
Sources and next steps
- onsemi: active cables and electronically marked assembliesPassive identity electronics versus active signal conditioning. Its design examples are not universal cable-length or power limits.
- Cable Matters 201034 manualExact-model HOST/SINK direction example; not a universal active-cable rule.
- USB-IF cable compliance updatesCurrent certified power/data markings and the legacy 100 W boundary.
- Plugable: cable certification and e-marker checksIdentity data is one part of electrical and interoperability testing.
Select requirementsDecode a claimCheck the data pathUSB-IF cable page