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USB Type-C is a 24-contact, reversible connector system. The pinout is fixed, but the capabilities are not: a USB-C port may implement only USB 2.0 + charging, or it may also implement USB 3.2, USB4, USB Power Delivery (PD), and Alternate Modes such as DisplayPort. In other words, USB-C defines the connector, not automatically the data rate or power level. (usb.org)
USB-C receptacle pin assignment
(front view, looking into the device receptacle)
| Pin | Signal | Function | Pin | Signal | Function |
|---|---|---|---|---|---|
| A1 | GND | Ground return | B12 | GND | Ground return |
| A2 | TX1+ | SuperSpeed transmit pair 1 | B11 | RX1+ | SuperSpeed receive pair 1 |
| A3 | TX1− | SuperSpeed transmit pair 1 | B10 | RX1− | SuperSpeed receive pair 1 |
| A4 | VBUS | Bus power | B9 | VBUS | Bus power |
| A5 | CC1 | Configuration Channel 1 | B8 | SBU2 | Sideband Use 2 |
| A6 | D+ | USB 2.0 pair, position 1 | B7 | D− | USB 2.0 pair, position 2 |
| A7 | D− | USB 2.0 pair, position 1 | B6 | D+ | USB 2.0 pair, position 2 |
| A8 | SBU1 | Sideband Use 1 | B5 | CC2 | Configuration Channel 2 |
| A9 | VBUS | Bus power | B4 | VBUS | Bus power |
| A10 | RX2− | SuperSpeed receive pair 2 | B3 | TX2− | SuperSpeed transmit pair 2 |
| A11 | RX2+ | SuperSpeed receive pair 2 | B2 | TX2+ | SuperSpeed transmit pair 2 |
| A12 | GND | Ground return | B1 | GND | Ground return |
This mapping comes from the USB-IF Type-C receptacle table. The official naming is TXp1/TXn1, RXp1/RXn1, Dp1/Dn1, etc.; the table above uses the more familiar +/− notation. (usb.org)
Key points
USB-C is best understood as five signal groups sharing one connector:
USB-C provides four VBUS contacts and four ground contacts. In a compliant implementation these are bussed together so the connector can carry higher current with acceptable contact heating and lower effective resistance. The Type-C spec’s DC requirements list 40 mΩ maximum initial low-level contact resistance and a contact-current test based on 5 A collectively on VBUS, plus current on the other contacts as applicable. (usb.org)
A subtle but important point is that VBUS is not supposed to be treated as “always present” in a native USB-C attachment. The USB-IF text states that VBUS is present only when a valid Source-to-Sink connection over the CC channel has been established. That is why CC handling is mandatory in a correct USB-C design. (usb.org)
The Configuration Channel pins, CC1 and CC2, are what make USB-C reversible and role-aware. They are used for:
Without USB PD, Type-C still supports current advertisement levels beyond legacy USB default power. USB-IF material shows the power precedence as:
USB PD communication itself is carried over the CC wire using BMC signaling. That PD channel is what negotiates voltages and currents beyond the default 5 V attachment behavior. (usb.org)
USB-C keeps backward compatibility with USB 2.0 by providing two D+/D− positions in the receptacle, one for each plug orientation. The USB-IF receptacle table labels them Dp1/Dn1 and Dp2/Dn2. However, in a cable there is typically only one USB 2.0 wire pair, and the receptacle side handles the flip condition. The official Type-C note explicitly says that B6 and B7 should not be present in the USB Type-C plug. (usb.org)
That point corrects a common oversimplification: a “24-pin connector” does not mean a standard cable always contains 24 independently wired end-to-end conductors. For USB 2.0 operation, the cable implementation is intentionally simpler. (usb.org)
The four high-speed differential pairs are:
These lanes support:
USB-IF’s 2022 USB4 Version 2.0 announcement also states support for up to 120 Gb/s in one direction while retaining 40 Gb/s in the other direction for asymmetric operation. (usb.org)
The SBU1/SBU2 pins are reserved for low-speed sideband functions. USB-IF material identifies them as Sideband Use, and notes that for USB4 they are used for SBTX/SBRX sideband signaling. When Alternate Modes are supported, USB PD Structured VDMs are used to discover, configure, and enter/exit those modes. (usb.org)
In practice, this is how protocols such as DisplayPort Alt Mode are enabled over the USB-C connector. The key engineering takeaway is that Alternate Mode is not automatic just because the connector is USB-C; the product must explicitly support it and negotiate it over PD. (usb.org)
As of May 7, 2026, the publicly searchable USB-IF material still points to the familiar public Type-C Release 2.0 pin table for the receptacle layout, while USB-IF compliance updates reference later base-spec updates such as Release 2.1 and a Type-C r2.3 ECN for contact-current clarification in March 2025. The pinout itself is stable; what has evolved more recently is certification policy, high-power support, and cable labeling. (usb.org)
The two most important modern changes are:
USB-IF compliance policy also now requires certified USB-C to USB-C cables to be marked with their power capability and, except for high-speed USB 2.0-only cables, their data-rate capability. (compliance.usb.org)
| Item | Practical meaning |
|---|---|
| Connector type | 24-contact reversible connector |
| USB 2.0 speed | Up to 480 Mb/s |
| USB 3.2 speeds | 5, 10, 20 Gb/s |
| USB performance branding now used by USB-IF | 5, 10, 20, 40, 80 Gb/s |
| USB4 v2 asymmetric mode | Up to 120 Gb/s one-way / 40 Gb/s reverse |
| Type-C current levels without PD | Default USB power, 1.5 A, 3.0 A |
| USB PD current | Up to 5 A |
| USB PD 3.1 EPR | Up to 240 W |
| Durability | 10,000 mating cycles minimum |
| Initial contact resistance | 40 mΩ max |
This summary is compiled from USB-IF specification excerpts, product-guideline documents, and compliance updates. (usb.org)
A USB 2.0 Type-C cable physically does not support USB 3.2 or USB4 signaling, and its TX/RX and SBU signals are not implemented. So two devices with USB-C connectors may still link only at USB 2.0 speeds if the cable is the limiting element. (usb.org)
From a compliance perspective, USB-IF states that a product with a USB Type-C connector shall only use USB-defined signaling methods to negotiate power over that connector. In other words, proprietary charging tricks over CC are not acceptable for certified USB-C products. (compliance.usb.org)
For safety and user transparency, certified cables are expected to carry appropriate power and performance markings. This matters especially for 240 W / EPR applications, where cable quality, e-marking, and certification are not optional from a responsible engineering standpoint. (usb.org)
One nuance in public USB-IF search results is that the most easily accessible full pin table is still associated with the August 2019 Release 2.0 Type-C document, while more recent USB-IF compliance pages reference 2021–2025 updates. That does not create ambiguity in the pin assignment itself; it mainly affects certification requirements, cable classes, contact-current clarifications, and product labeling. (usb.org)
If you want to go deeper, the next useful documents to study are:
If you want, I can next provide either: