USB‑C plugUSB‑C receptacle on a laptop with the legacy SuperSpeed (usually USB 5Gbps) logo
USB‑C, or USB Type‑C, is a 24-pin reversible connector (not a protocol) that supersedes all previous USB connectors, which were designated legacy in 2014. This connector also supersedes Mini DisplayPort and Lightning[3] connectors. USB-C is widely used for multiple purposes: exchanging data with peripheral devices, such as external drives, mobile phones, keyboards, trackpads, and mice, and between hosts; transferring A/V-data to displays and speakers; and powering peripheral devices and being powered by power adapters, either through directly wired connectors or indirectly via hubs and docking stations. This connector type can be used for other data transfer protocols besides USB, such as Thunderbolt, PCIe, DisplayPort, and HDMI. It is extensible, allowing the support of future protocols.
The design for the USB‑C connector was initially developed in 2012 by members of the USB Implementers Forum, with Intel, HP Inc., and Texas Instruments being distinguished on the design document, though Apple Inc. and Microsoft, among others, also contributed. The Type‑C Specification 1.0 was published by the USB Implementers Forum (USB-IF) on August 11, 2014.[4] In 2016 it was adopted by the International Electrotechnical Commission as IEC62680-1-3.
The USB Type‑C connector has 24 pins and is reversible.[5][6] The designation C distinguishes it from the various USB connectors it replaced, all termed Type‑A, Type‑B, or, for receptacles only, Type‑AB. Whereas every earlier valid USB cable had a host end A and a peripheral device end B, a USB‑C cable connects either way (and the devices handle the logical A–B distinction). For interoperation with older equipment, there are Type-C-to-legacy cables; such a cable has a Type‑C plug at one end and either a Type‑A (host) or a Type‑B (peripheral device) plug at the other.
The designation C (Type-C or USB-C) refers only to the connector's physical configuration, or form factor, not to be confused with a cable or port's specific capabilities and performance, such as Thunderbolt 3, DisplayPort 2.0, or USB 3.2 Gen 2×2. While USB‑C is the single modern connector for all USB protocols, there are valid uses of the connector that do not involve any USB protocol. Depending on the protocols supported by all connected devices–host, intermediate devices (hubs), and peripheral devices–a USB‑C connection can provide much higher data rates and electrical power than anything using the superseded connectors.
A device with a Type‑C connector does not necessarily implement any USB transfer protocol, USB Power Delivery, or any of the Alternate Modes: the Type‑C connector is common to several technologies while mandating only a few of them.[7]
USB 3.2, released in September 2017, fully replaced the USB 3.1 (and therefore also USB 3.0) specifications. It preserves the former USB3.1 SuperSpeed and SuperSpeedPlus architectures and protocols, with transfer rates of 5 and 10Gbit/s, and introduces two two-lane operational modes with the same signalling rates in each lane, doubling the transfer rates to 10 and 20Gbit/s. These are only applicable with Full-Featured USB‑C cables and hosts, hubs, and peripheral devices that use them.
Jurisdictions with legal requirements of USB-C power ports for most 5–20V (maximum 100W) consumer devices
The USB4 specification, released in 2019, is the first USB protocol standard that is applicable exclusively via USB‑C.
Ease of use
The USB‑C standard simplifies usage by specifying cables having identical plugs on both ends; orientation is moot. Also, the plugs are flat but can be inserted in either orientation.
Symmetry
Mechanically, USB‑C receptacles have two-fold rotational symmetry–a plug may be inserted into a receptacle in either of two orientations.
Electrically, USB‑C plugs are not symmetrical, as can be seen in the tables of pin layouts. Also, some contacts are wired straight through and some are crossed over, as shown in the table of cable wiring.
Though a Type‑C–Type‑C cable is symmetrical, the connected devices still have logical host (A) and peripheral device (B) roles. If both devices are only capable of the same role, no damage occurs but no link is established; if both devices are capable of both roles, they negotiate to determine which takes which role. Determination of this host-to-peripheral-device relationship is accomplished through a Configuration Channel (CC) that is connected through the cable.[8]
Universal application
The USB‑C standard attempts to eliminate the need to have different cables for other communication technologies, such as Thunderbolt, PCIe, HDMI, DisplayPort and more. Since the introduction in 2014, many companies have adopted the USB‑C standard into their products.[3] USB‑C cables can contain circuit boards and processors, giving them much more capability than simple circuit connections.
Overview
USB‑C cables interconnect hosts and peripheral devices, replacing various other electrical cables and connectors, including all earlier (legacy) USB connectors, HDMI connectors, DisplayPort connectors, and 3.5mm audio jacks.[9][10]
USB Type‑C and USB‑C are trademarks of the USB Implementers Forum, Inc.[11]
The 24-pin double-sided connector is slightly larger than the non-SuperSpeed, USB 2.0 Micro connectors, with a USB‑C receptacle opening measuring 8.34mm× 2.56mm, 6.20mm deep.
Cables
This section needs to be updated. The reason given is: the whole cable sections in this article is incomplete, full of errors, hear saying, and not up-to-date;. Please help update this article to reflect recent events or newly available information.(August 2024)
Type‑C cables can be split among various categories and subcategories. The first one is USB 2.0 vs Full-Featured. USB 2.0 Type‑C cables have very limited wires and are only good for USB1 and USB2 communications and Power Delivery. They are also called charging cables colloquially. Conversely, Full-Featured cables need to have all wires populated and in general support Alternate Modes, and they are further distinguished by their speed ratings.
Full-Featured cables exist in different speed grades. Their technical names, the operation modes, use the Gen x notation, each higher number expressing increasing capabilities in terms of data rate. The marketing names are based on the nominal data rates: "USB 5Gbps", "USB 10Gbps", "USB 20Gbps", "USB 40Gbps", and so on. Full-Featured cables can support at least USB 3.x, USB Power Delivery and DisplayPort.
A Gen1 (signalling rate of 5Gbit/s) cable supports the Gen1 rate on each of its two lanes (2× 2 twisted data wire pairs). It can be used to establish a USB3.2 Gen1×2 operation mode with nominally 10Gbit/s (2× 5 Gbit/s) between two devices capable of USB 3.2 or later connected with a Full-Featured USB-C cable.
According to the USB41.0 and 2.0 specifications, implementation of the USB3.2 Gen2×2 operation mode, resulting in nominally 20Gbit/s, is optional; indeed most USB4 controllers do not implement it. In other words, the "USB 20Gbps" will only be achieved by a USB4 or more modern version of an operation mode, such as USB4 Gen2×2, with USB4-capable devices and Full-Featured USB-C cables (and intermediate hubs) of a rate of "USB 20Gbps" (i.e. all four twisted data-wire pairs are wired) or higher between a host and a peripheral device.
The USB Implementers Forum certifies valid cables so they can be marked accordingly with the official logos and users can distinguish them from non-compliant products.[12] There have been simplifications in the logos.[13] Previous logos and names also referenced specific USB protocols like SuperSpeed for the USB 3 family of connections or USB4 directly. The current official names and logos have removed those references as most full-featured cables can be used for USB4 connections as well as USB3 connections.
In order to achieve greater cable lengths, cable variants with active electronics to amplify the signals also exist. The Type‑C standard mostly mandates that these active cables behave similarly to passive cables with vast backwards compatibility, but they are not required to support all possible features and typically have no forward compatibility to future standards. Optical cables are even allowed to further reduce the backwards compatibility. For example, an active cable may not be able to use all high-speed wire pairs in the same direction (as used for DisplayPort connections) but only in the symmetric combinations expected by classic USB connections. Passive cables have no such limitations.
Every USB‑C cable must support at least three amps of current and up to 20 volts, for up to 60 watts of power, according to the USB Power Delivery (PD) specification. Cables were also allowed to support up to 5A while retaining the 20V limit, allowing up to 100W of power; however, the 20V limit for 5A cables has been deprecated in favor of 48V. The combination of 48V support and 5A current support is called Extended Power Range (EPR) and allows for up to 240W (48V× 5A) of power according to the USB PD specification.
eMarker
Each Type‑C cable except the most basic, supporting only up to USB 2.0 and 60W (20V× 3A), must contain electronics, called an eMarker in the standard, that identify the cable and its capabilities via the Configuration Channel (CC). This identification data includes information about product and vendor, cable connectors, supported USB signalling protocols (USB 2.0, USB 3.x, etc), passive vs active construction, use of VCONN power, available VBUS voltages and currents, latency, transmit vs receive directionality, SOP controller mode, and hardware and firmware versions.[14] It also can include further vendor-defined messages (VDM) that detail support for Alternate Modes or vendor-specific functionality outside of the USB standards.
Hosts and peripheral devices
For any two pieces of equipment connecting over USB, one is a host (with a downstream-facing port, DFP) and the other is a peripheral device (with an upstream-facing port, UFP). Some products, such as some mobile phones, can take either role, whichever is opposite that of the connected equipment. Such equipment is said to have Dual-Role-Data (DRD) capability, which was known as USB On-The-Go in earlier specifications.[15] With USB‑C, when two such devices are connected, the roles are first randomly assigned, but a swap can be commanded from either end, although there are optional path and role detection methods that would allow equipment to select a preference for a specific role. Furthermore, Dual-Role equipment that implements USB Power Delivery may swap data and power roles independently using the Data Role Swap and Power Role Swap processes. This allows for charge-through hub and docking station applications such as a portable computer acting as a host to connect to peripherals but being powered by the dock, or a computer being powered by a display, through a single USB‑C cable.[7]
USB‑C devices may optionally provide or consume bus power currents of 1.5A and 3.0A (at 5V) in addition to baseline bus power provision; power sources can either advertise increased USB current through the configuration channel or implement the full USB Power Delivery specification using both the BMC-coded configuration line and the legacy BFSK-coded VBUS line.[7][16]
All USB connectors aside from Type-C (that is, all 23 Type‑A and Type‑B connectors) are designated legacy. Connecting legacy and modern, USB‑C equipment requires either a legacy cable assembly (a cable with either Standard‑A plug or any Type‑B plug at one end and a Type‑C plug at the other) or, in very specific cases, a legacy adapter assembly.
An older device can connect to a modern (USB‑C) host by using a legacy cable with a Type-C plug on the host (A) end and any Type-B plug (Standard-B, Mini-B, or Micro-B) on the peripheral (B) end. Similarly, a modern peripheral device can connect to a legacy host by using a legacy cable with a USB‑C plug on the peripheral device (B) end and a (USB 2 or USB 3) Standard-A plug on the host (A) end. Legacy adapters with USB‑C receptacles are "not defined or allowed" by the specification because they can create "many invalid and potentially unsafe" cable combinations (being generally any cable assembly with two A ends or two B ends). However, exactly two types of USB adapters with Type‑C plugs are defined: An adapter with a USB 3 Standard‑A receptacle (for connecting a legacy device to a modern host, supporting up to 10Gbit/s), and one with a Micro‑B receptacle (for connecting a modern device to a legacy host or power supply, supporting up to USB 2).[17]
Non-USB modes
Liquid Corrosion Mitigation Mode
This is an optional mode that aims to reduce the risk of corrosion within the Type-C port by driving voltages down as close as possible to 0V.
Debug Accessory Mode
This mode can be used for both high-level and low-level debugging purposes. For embedded devices this can be used to allow access to e.g. a JTAG Test Access Port without having to open the casing of a device. It is designed for usage both within LAB and within production environments. Basic debug requirements are defined as a standard feature and are therefore present in all compliant devices. A vendor may add debug features as required. The spec demands the assurance by the vendor that an explicit user authorization and the actual vendor specific implementation do not compromise system security or user privacy. Also noteworthy is that detecting the orientation of the cable is optional for this mode, meaning it may only work when the cable is plugged in in a given orientation but not in the reverse.
To enter this mode the device needs to detect both CC pins being terminated using pull-up, or both with pull-down, resistors. Because this mode uses both CC pins a receptacle-to-receptacle connection using a compliant Type-C-to-Type-C cable cannot be detected. This is because the spec does not allow USB-C cables to connect both CC wires through and requires that CC2, a.k.a. VCONN, be isolated instead. Therefore, a captive cable (that is, one in which one end either is hard-wired or has a proprietary connector), a directly attaching device (something that connects without a cable), or a non-compliant cable that connects both CC contacts through is needed.
An Alternate Mode dedicates some of the physical wires in a USB‑C cable for direct device-to-host transmission using non-USB data protocols, such as DisplayPort or Thunderbolt. The four high-speed lanes, two side-band pins, and (for devices that connect directly or with captive cables) five additional pins can be used for Alternate Mode purposes. The modes are configured using vendor-defined messages (VDMs) through the configuration channel.
Audio Adapter Accessory Mode (deprecated)
Deprecated in October 2024, with the Type‑C Cable and Connector Specification version 2.3,[18] to allow for the new Liquid Corrosion Mitigation Mode, this mode allowed a device with a Type‑C receptacle to support analog headsets directly through an audio adapter with a 3.5mm jack, providing three analog audio channels (left and right output and a monaural microphone input). Unlike superficially similar Lightning adapters, which handle all analog conversion and audio amplification internally, the adapters that used this Accessory Mode contained no electronics and required that the host device have all the additional components to handle analog audio–digital-to-analog converters and amplifiers for audio output and an analog-to-digital converter to handle the analog microphone signal. Such an adapter could optionally include a USB‑C charge-through port to allow 500mA device charging. The engineering specification states that an analog headset shall not use a USB‑C plug instead of a 3.5mm plug. In other words, a headset with a USB‑C plug must always support digital audio (but optionally could support the Accessory Mode).[19]
Analog signals used the USB2.0 differential pair contacts (Dp and Dn for right and left) and the two Sideband Use (SBU) contacts for microphone and ground. The presence of the audio accessory was signaled through the configuration channel and VCONN.
With the deprecation of Audio Adapter Accessory Mode, the Type-C specification strongly recommends using USB Audio Device Class 4.0 while also recommending version 2.0.[20]
Specifications
USB Type‑C cable and connector specifications
The USBType‑C specification, release 1.0, was published by the USB Implementers Forum (USB-IF) and was finalized in August 2014.[21][10]
It defines requirements for cables and connectors.
Release 2.0 was published 2019-08-29, primarily for enabling USB4.[28]
Release 2.1 was published 2021-05-25, primarily for enabling the USB Power Delivery Extended Power Range: 240W (as 48V × 5A).[29]
Release 2.2 was published 2022-10-18, primarily for enabling USB 80Gbps (USB4 Version 2.0).[17]
Release 2.3 was published 2023-10-31, primarily for deprecating the Audio Adapter Accessory Mode and replacing it with the Liquid Corrosion Mitigation Mode, and for updating the Multi-port Charger Shared Capacity definition and behaviors.[30]
IEC 62680-1-3:2016 (2016-08-17, edition 1.0) "Universal serial bus interfaces for data and power – Part 1-3: Universal Serial Bus interfaces – Common components – USB Type‑C cable and connector specification"[33][34]
IEC 62680-1-3:2017 (2017-09-25, edition 2.0) "Universal serial bus interfaces for data and power – Part 1-3: Common components – USB Type‑C Cable and Connector Specification"[35]
IEC 62680-1-3:2018 (2018-05-24, edition 3.0) "Universal serial bus interfaces for data and power – Part 1-3: Common components – USB Type‑C Cable and Connector Specification"[36]
Receptacles
Type‑C receptacle pinout (end-on view)
The receptacle features four power and four ground pins, two differential pairs (connected together on devices) for legacy USB 1 (1.5 and 12Mbit/s half-duplex) and 2 (480Mbit/s half-duplex) data, four shielded differential pairs for Enhanced SuperSpeed data (two transmit and two receive pairs), two Sideband Use (SBU) pins, and two Configuration Channel (CC) pins.
12In USB-C cables, the differential pair for legacy, non-SuperSpeed data is wired only to pins A6 and A7, while B6 and B7 are absent or unwired. In the receptacle A6 and B6, and A7 and B7, are wired together; therefore the plug's orientation does not matter, connecting the plug's legacy data pair (A6, A7) either to the receptacle's A6 and A7 or, equivalently, to its B6 and B7.
Plugs
Type‑C plug pinout (end-on view)
The plug has only one USB 2.0 high-speed differential pair, and one of the Configuration Channel pins (CC2) is replaced by VCONN, to power optional electronics in the cable, and the other is used to actually carry the Configuration Channel signals. These signals are used to determine the orientation of the cable as well as to carry USB Power Delivery communications.
Cables
Although plugs have 24 pins, cables commonly have only 18 wires. In the following table, the "No." column shows the wire number as assigned within the spec. It is allowed to use multiple wires instead of a single wire. The spec does not demand having two GND and VBUS wires even though it allocated a wire number for them. Note that within the plugs all of the VBUS wires must be joined together. The same is true for all of the GND wires (including shielding).
↑VCONN must not traverse end-to-end through the cable. Some isolation method must be used. Can also be terminated directly within the plugs at both ends without a connecting wire in between. There are exceptions for cases where the USB-C wire is directly connected to a device at one end to allow these devices to be powered through VCONN. Thereby it is basically the active component within the cable which allows to work around the restriction of USB-C cables not being allowed to Backfeed power VCONN into connected devices.
12There is only a single differential pair for non-SuperSpeed data in the cable, which is connected to A6 and A7. Contacts B6 and B7 should not be present in the plug.
12345678Wire colors for differential pairs are not mandated.
Related USB-IF specifications
USB Type‑C Locking Connector Specification
The USB Type‑C Locking Connector Specification was published 2016-03-09. It defines the mechanical requirements for USB‑C plug connectors and the guidelines for the USB‑C receptacle mounting configuration to provide a standardized screw lock mechanism for USB‑C connectors and cables.[37]
USB Type‑C Port Controller Interface Specification
The USB Type‑C Port Controller Interface Specification was published 2017-10-01. It defines a common interface from a USB‑C Port Manager to a simple USB‑C Port Controller.[38]
USB Type‑C Authentication Specification
Adopted as IEC specification: IEC 62680-1-4:2018 (2018-04-10) "Universal Serial Bus interfaces for data and power–Part 1-4: Common components–USBType-C Authentication Specification"[39]
USB 2.0 Billboard Device Class Specification
USB 2.0 Billboard Device Class is defined to communicate the details of supported Alternate Modes to the computer host OS. It provides user readable strings with product description and user support information. Billboard messages can be used to identify incompatible connections made by users. They optionally appear to negotiate multiple Alternate Modes and must appear when negotiation fails between the host (source) and device (sink).
USB Audio Device Class 3.0 Specification
USB Audio Device Class 3.0 defines powered digital audio headsets with a USB‑C plug.[7] The standard supports the transfer of both digital and analog audio signals over the USB port.[40]
While it is not necessary for USB‑C compliant devices to implement USB Power Delivery, for USB‑C DRP/DRD (Dual-Role-Power/Data) ports, USB Power Delivery introduces commands for altering a port's power or data role after the roles have been established when a connection is made.[41]
USB 3.2 Specification
USB 3.2, released in September 2017, replaces the USB3.1 specification. It preserves existing USB3.1 SuperSpeed and SuperSpeed+ data modes and introduces two new SuperSpeed+ transfer modes over the USB‑C connector using two-lane operation, doubling the signalling rates to 10 and 20Gbit/s (raw data rate 1 and ~2.4GB/s).
USB4 Specification
The USB4 specification released in 2019 is the first USB data transfer specification to be exclusively applicable by the Type‑C connector.
Alternate Mode partner specifications
As of 2018, five system-defined Alternate Mode partner specifications exist. Additionally, vendors may support proprietary modes for use in dock solutions. Alternate Modes are optional; Type‑C features and devices are not required to support any specific Alternate Mode, nor are they required to support USB (though some standards using Alternate Modes, such as Thunderbolt, require that all compatible ports support USB communications as well). The USB Implementers Forum is working with its Alternate Mode partners to make sure that ports are properly labelled with respective logos.[42]
Other protocols, like Ethernet,[62] have been proposed, although Thunderbolt 3 and later are also capable of 10 Gigabit Ethernet networking.[63]
All Thunderbolt 3 controllers support both Thunderbolt Alternate Mode and DisplayPort Alternate Mode.[64] Because Thunderbolt can encapsulate DisplayPort data, every Thunderbolt controller can either output DisplayPort signals directly over DisplayPort Alternative Mode or encapsulated within Thunderbolt in Thunderbolt Alternate Mode. Low-cost peripherals mostly connect via DisplayPort Alternate Mode while some docking stations tunnel DisplayPort over Thunderbolt.[65]
DisplayPort Alternate Mode does not support DisplayPort Dual-Mode (DP++), which allows DisplayPort sources to output HDMI-compatible signals. As a result, USB Type‑C-to-HDMI adapters or cables which use DisplayPort Alternate Mode must incorporate active conversion circuitry.[66] DisplayPort Alternate Mode 2.0: DisplayPort 2.0 can run directly over USB‑C alongside USB4. DisplayPort 2.0 can support 8K resolution at 60Hz with HDR10 color and can use up to 80Gbps, which is double the amount available to USB data.[67]
As of 2023 there were no known USB Type-C-to-HDMI adapters using HDMI Alternate Mode, according to the HDMI Licensing Association.[68]
The USB SuperSpeed protocol is similar to DisplayPort and PCIe/Thunderbolt, in using packetized data transmitted over differential LVDS lanes with embedded clock using comparable bit rates, so these Alternate Modes are easier to implement in the chipset.[47]
Alternate Mode hosts and peripheral devices can be connected with either regular Full-Featured Type‑C cables, or with converter cables or adapters:
USB 3.1 Type‑C to Type‑C Full-Featured cable
DisplayPort, Mobile High-Definition Link (MHL), HDMI and Thunderbolt (20Gbit/s, or 40Gbit/s with cable length up to 0.5m) Alternate Mode Type‑C ports can be interconnected with standard passive Full-Featured USB Type‑C cables. These cables are only marked with standard "trident" SuperSpeed USB logo (for Gen1 mode only) or the SuperSpeed+ USB 10Gbit/s logo on both ends.[69] Cable length should be 2.0m or less for Gen1 and 1.0m or less for Gen2.
Thunderbolt3 (40Gbit/s) Alternate Mode with cables longer than 0.8m requires active Type‑C cables that are certified and electronically marked for high-speed Thunderbolt3 transmission, similarly to high-power 5A cables.[43][46] These cables are marked with a Thunderbolt logo on both ends. They do not support USB3 backwards compatibility, only USB2 or Thunderbolt. Cables can be marked for both Thunderbolt and 5A power delivery at the same time.[70]
Active cables and adapters contain powered electronics to allow for longer cables or to perform protocol conversion. The adapters for video Alternate Modes may allow conversion from native video stream to other video interface standards (e.g., DisplayPort, HDMI, VGA or DVI).
Using Full-Featured Type‑C cables for Alternate Mode connections provides some benefits. Alternate Mode does not employ USB2.0 lanes and the configuration channel lane, so USB2.0 and USB Power Delivery protocols are always available. In addition, DisplayPort and MHL Alternate Modes can transmit on one, two, or four SuperSpeed lanes, so two of the remaining lanes may be used to simultaneously transmit USB3.1 data.[71]
Alternate Mode protocol support matrix for Type‑C cables and adapters
↑USB 2.0 and USB Power Delivery are available at all times in a Type‑C cable
↑USB 3.1 can be transmitted simultaneously when the video signal bandwidth requires two or fewer lanes.
12Is only available in Thunderbolt3 DisplayPort mode
↑Thunderbolt3 40Gbit/s passive cables are only possible <0.8m due to limitations of current cable technology.
USB‑C receptacle pin usage in different modes
The diagrams below depict the pins of a USB‑C receptacle in different use cases.
USB 2.0/1.1
A simple USB 2.0/1.1 device mates using one pair of D+/D− pins. Hence, the source (host) does not require any connection management circuitry, but it lacks the same physical connector so therefore USB‑C is not backward compatible. VBUS and GND provide 5V up to 500mA of current.
However, to connect a USB2.0/1.1 device to a USB‑C host, use of pull-down resistors Rd[72] on the CC pins is required, as the source (host) will not supply VBUS until a connection is detected through the CC pins.
GND
TX1+
TX1−
VBUS
CC1
D+
D−
SBU1
VBUS
RX2−
RX2+
GND
GND
RX1+
RX1−
VBUS
SBU2
D−
D+
CC2
VBUS
TX2−
TX2+
GND
USB Power Delivery
The USB Power Delivery specification uses one the CC pins for power negotiation between source device and sink device. It is transparent to any data transmission mode and can therefore be used together with any of them as long as the CC pins are intact.
An extension to the specification has added 28V, 36V and 48V to support up to 240W of power.[73]
GND
TX1+
TX1−
VBUS
CC1
D+
D−
SBU1
VBUS
RX2−
RX2+
GND
GND
RX1+
RX1−
VBUS
SBU2
D−
D+
CC2
VBUS
TX2−
TX2+
GND
USB 3.2
In the USB 3.2 mode, two or four high speed links are used in TX/RX pairs to provide 5, 10, or 20Gbit/s (only by USB 3.2 two-lane operations) signalling rates respectively. One of the CC pins is used to negotiate the mode.
VBUS and GND provide 5V up to 900mA, in accordance with the USB3.1 specification. A specific USB‑C mode may also be entered, where 5V at nominal either 1.5A or 3A is provided.[74] A third alternative is to establish a USB Power Delivery (USB‑PD) contract.
In single-lane mode, only the differential pairs closest to the CC pin are used for data transmission. For dual-lane data transfers, all four differential pairs are in use.
The D+/D− link for USB2.0/1.1 is typically not used when a USB3.x connection is active, but devices like hubs open simultaneous 2.0 and 3.x uplinks in order to allow operation of both types of devices connected to it. Other devices may have the ability to fall back to 2.0, in case the 3.x connection fails. For this, it is important that SS and HS lanes are correctly aligned so that e.g. operating system messages indicating overcurrent conditions report the correct shared USB plug.
GND
TX1+
TX1−
VBUS
CC1
D+
D−
SBU1
VBUS
RX2−
RX2+
GND
GND
RX1+
RX1−
VBUS
SBU2
D−
D+
CC2
VBUS
TX2−
TX2+
GND
Alternate Modes
In Alternate Modes one of up to four high speed links are used in whatever direction is needed. SBU1, SBU2 provide an additional lower speed link. If two high speed links remain unused, then a USB3.2 link can be established concurrently to the Alternate Mode.[48] One of the CC pins is used to perform all the negotiation. An additional low band bidirectional channel (other than SBU) may share that CC pin as well.[48][56] USB2.0 is also available through D+/D− pins.
In regard to power, the devices are supposed to negotiate a Power Delivery contract before an Alternate Mode is entered.[75]
GND
TX1+
TX1−
VBUS
CC1
D+
D−
SBU1
VBUS
RX2−
RX2+
GND
GND
RX1+
RX1−
VBUS
SBU2
D−
D+
CC2
VBUS
TX2−
TX2+
GND
Debug Accessory Mode
The external device test system (DTS) signals to the target system (TS) to enter debug accessory mode via CC1 and CC2 both being pulled down with an Rd resistor value or pulled up as Rp resistor value from the test plug (Rp and Rd defined in Type‑C specification).
After entering debug accessory mode, optional orientation detection via the CC1 and CC2 is done via setting CC1 as a pullup of Rd resistance and CC2 pulled to ground via Ra resistance (from the test system Type‑C plug). While optional, orientation detection is required if USB Power Delivery communication is to remain functional.
In this mode, all digital circuits are disconnected from the connector, and the 14 bold pins can be used to expose debug related signals (e.g. JTAG interface). USB IF requires for certification that security and privacy consideration and precaution has been taken and that the user has actually requested that debug test mode be performed.
GND
TX1+
TX1−
VBUS
CC1
D+
D−
SBU1
VBUS
RX2−
RX2+
GND
GND
RX1+
RX1−
VBUS
SBU2
D−
D+
CC2
VBUS
TX2−
TX2+
GND
If a reversible Type‑C cable is required but Power Delivery support is not, the test plug will need to be arranged as below, with CC1 and CC2 both being pulled down with an Rd resistor value or pulled up as Rp resistor value from the test plug:
GND
TS1
TS2
VBUS
CC1
TS6
TS7
TS5
VBUS
TS4
TS3
GND
GND
TS3
TS4
VBUS
TS5
TS7
TS6
CC2
VBUS
TS2
TS1
GND
This mirroring of test signals will only provide seven test signals for debug usage instead of fourteen, but with the benefit of minimizing extra parts count for orientation detection.
Audio Adapter Accessory Mode
This mode was deprecated in 2023 to allow for Liquid Corrosion Mitigation Mode.[30] In Audio Adapter Accessory Mode all digital circuits were disconnected and certain pins were reassigned for analog outputs or inputs. The mode, where supported, was invoked when both CC pins were shorted to GND. D− and D+ became audio output left (L) and right (R), respectively. The SBU pins became a microphone pin (MIC) and the analog audio ground (AGND), the latter being a return path for both outputs and the microphone. Nevertheless, the MIC and AGND pins had to have automatic swap capability for two reasons: firstly, the USB‑C plug could be inserted in either orientation; secondly, there was no agreement which TRRS contacts should be GND and MIC, so devices equipped with a headphone jack with microphone input must be able to perform this swap anyway.[76]
This mode also allowed concurrent charging of a device exposing the analog audio interface (through VBUS and GND), however, only at 5V and 500mA, as CC pins were unavailable for any negotiation.
GND
TX1+
TX1−
VBUS
CC1
R
L
MIC
VBUS
RX2−
RX2+
GND
GND
RX1+
RX1−
VBUS
AGND
L
R
CC2
VBUS
TX2−
TX2+
GND
Plug insertions detection is performed by the TRRS plug's physical plug detection switch. On plug insertions, this will pull down both CC and VCONN in the plug (CC1 and CC2 in the receptacle). This resistance must be less than 800ohms, the minimum "Ra" resistance specified in the USB Type‑C specification). This is essentially a direct connection to USB digital ground.
TRRS contact wiring to Type‑C plug (Figure A-2 of USB Type‑C Cable and Connector Specification Release 1.3)
An increasing number of motherboards, notebooks, tablet computers, smartphones, hard disk drives, USB hubs and other devices released from 2014 onwards include the USB‑C receptacles. However, the initial adoption of USB‑C was limited by the high cost of USB‑C cables[86] and the wide use of Micro-USB chargers.
Video output
A USB‑C multiport adapter converts the device's native video stream to DisplayPort/HDMI/VGA, allowing it to be displayed on an external display, such as a television set or computer monitor.
It is also used on USB‑C docks designed to connect a device to a power source, external display, USB hub, and optional extra (such as a network port) with a single cable. These functions are sometimes implemented directly into the display instead of a separate dock,[87] meaning a user connects their device to the display via USB‑C with no other connections required.
Compatibility issues
Power issues with cables
Many cables claiming to support USB‑C are actually not compliant to the standard. These cables can, potentially, damage a device.[88][89][90] There are reported cases of laptops being destroyed due to the use of non-compliant cables.[91]
Some non-compliant cables with a USB‑C connector on one end and a legacy USB‑A plug or Micro-B receptacle (receptacles also usually being invalid on cables, but see known exceptions in the sections on Hosts and peripheral devices and, formerly, Audio Adapter Accessory Mode above) on the other end fail to be, or incorrectly terminate the Configuration Channel (CC) with a 10kΩ pull-up to VBUS instead of the specification-mandated 56kΩ pull-up,[92] causing a device connected to the cable to incorrectly determine the amount of power it is permitted to draw from the cable. Cables with this issue may not work properly with certain products, including Apple and Google products, and may even damage power sources such as chargers, hubs, or PC USB ports.[93][94]
A defective USB‑C cable or power source can cause a USB‑C device to see an incorrect and different "declared" voltage than what the source will actually deliver. This may result in an overvoltage on the VBUS pin.
Also due to the fine pitch of the USB‑C receptacle, the VBUS pin from the cable may contact with the CC pin of the USB‑C receptacle resulting in a short-to-VBUS electrical issue due to the fact that the VBUS pin is rated up to 20V while the CC pins are rated up to 5.5V.
To overcome these issues, USB Type‑C port protection must be used between a USB‑C connector and a USB‑C Power Delivery controller.[95]
Compatibility with audio adapters
The USB‑C port can be used to connect wired accessories such as headphones.
There are two modes of audio output from devices: digital and analog. There are primarily two types of USB‑C audio adapters: active, e.g. those with digital-to-analog converters (DACs), and passive, without electronics.[96][97]
When an active set of USB‑C headphones or adapter is used, digital audio is sent through the USB‑C port. The conversion by the DAC and amplifier is done inside of the headphones or adapter, instead of on the phone. The sound quality is dependent on the headphones/adapter's DAC. Active adapters with a built-in DAC have near-universal support for devices that output digital and analog audio, adhering to the Audio Device Class 3.0 and Audio Adapter Accessory Mode specifications.
Examples of such active adapters include external USB sound cards and DACs that do not require special drivers,[98] and USB‑C to 3.5mm headphone jack adapters by Apple, Google, Essential, Razer, HTC, and Samsung.[99]
On the other hand, when a passive adapter is used, digital-to-analog conversion is done on the host device and analog audio is sent through the USB‑C port. The sound quality is dependent on the phone's onboard DAC. Passive adapters are only compatible with devices that output analog audio, adhering to the Audio Adapter Accessory Mode specification.
USB‑C to 3.5mm audio adapters and USB sound cards compatibility
In 2016, Benson Leung, an engineer at Google, pointed out that Quick Charge 2.0 and 3.0 technologies developed by Qualcomm are not compatible with the USB‑C standard.[100] Qualcomm responded that it is possible to make fast-charge solutions fit the voltage demands of USB‑C and that there are no reports of problems; however, it did not address the standard compliance issue at that time.[101] Later in the year, Qualcomm released Quick Charge 4, which it claimed was – as an advancement over previous generations – "USBType‑C and USBPD compliant".[102]
In 2021, the European Commission proposed the use of USB‑C as a universal charging interface.[103][104][105] On 4 October 2022, the European Parliament voted in favor of the new law, Radio Equipment Directive 2022/2380, with 602 votes in favor, 13 against and 8 abstentions.[106] The regulation requires that all new mobile phones, tablets, cameras, headphones, headsets, handheld video game consoles, portable speakers, e-readers, keyboards, mice, portable navigation systems, and earbuds sold in the European Union and supporting wired charging, would have to be equipped with a USB‑C port and charge with a standard USB‑C cable by the end of 2024. Additionally, if these devices support fast charging, they must support USB Power Delivery. These regulations will extend to laptops by early 2026.[107] To comply with these regulations, Apple Inc. replaced its proprietary Lightning connector with USB‑C beginning with the iPhone 15 and AirPods Pro second generation, released in 2023.[108]
In late December 2024, new EU regulations took effect, mandating USB‑C charging ports for all small and medium-sized electronic devices sold in the EU, with laptops following on 28 April 2026.[109] These rules were aimed at reducing waste and saving €250 million annually for consumers. Apple, which initially opposed the changes, had since adopted USB‑C for its products. Additionally, consumers can opt not to receive a new charger with their device.[110]
Security
Authentication
USB Type‑C Authentication is an extension to the USB‑C protocol which can add security to the protocol.[111][112][113]
↑USB Type‑C® Cable and Connector Specification Release 2.4USB Type‑C 2.4 Release 202410.zip archive:
USB Type‑C Spec R2.4 - October 2024.pdf, p.27:
Revision History table:
row 2.3 – October 2023:
New release primarily for deprecating the Audio Adapter Accessory Mode and replacing it with the Liquid Corrosion Mitigation Mode, and for updating the Multi-port Charger Shared Capacity definition and behaviors. […]
↑Universal Serial Bus Type‑C Cable and Connector Specification Release 1.3 (14 July 2017), section A.1, page 213.
↑USB 3.0 Promoter Group (2015-04-03), Universal Serial Bus Type-C Cable and Connector Specification, Release 1.1{{citation}}: CS1 maint: numeric names: authors list (link)
↑"One common charging solution for all". Internal Market, Industry, Entrepreneurship and SMEs – European Commission. 2016-07-05. Archived from the original on 2021-10-19. Retrieved 2021-10-19.
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