View source for USB hardware

{{Short description|Communication connector using the USB protocol}}
{{Use American English|date=July 2024}}
{{Use mdy dates|date=July 2024|cs1-dates=y}}
[[File:Usb connectors.JPG|thumb|upright=1.5|Various legacy USB connectors along a centimeter ruler for scale.
{{Ordered list|Micro-B plug|Proprietary UC-E6 connector used on many older Japanese cameras for both USB and analog AV output|Mini-B plug|Standard-A receptacle (non-compliant because USB does not allow extension cables<ref name="USB 2.0 6.4.4">{{cite tech report |date=April 27, 2000 |title=Universal Serial Bus Specification |edition=Revision 2.0 |institution=USB-IF |at=6.4.4 Prohibited Cable Assemblies }}</ref>)|Standard-A plug|Standard-B plug}}]]

The initial versions of the [[USB]] standard specified connectors that were easy to use and that would have acceptable life spans; revisions of the standard added smaller connectors useful for compact portable devices. Higher-speed development of the USB standard gave rise to another family of connectors to permit additional data paths. All versions of USB specify cable properties; version 3.''x'' cables include additional data paths. The USB standard included [[power supply]] to [[peripheral]] devices; modern versions of the standard extend the power delivery limits for [[battery charging]] and devices requiring up to 240 [[watt]]s. USB has been selected as the standard charging format for many [[mobile phone]]s, reducing the proliferation of proprietary chargers.

== Connectors <span class="anchor" id="CONNECTORS"></span><span class="anchor" id="connector"></span>==
[[File:USB 2.0 and 3.0 connectors.svg|thumb|upright=1.5|Comparison of ''legacy'' USB connector plugs, omitting the current standard Type-C plugs]]

Unlike other data [[Bus (computing)|bus]]es (such as [[Ethernet]]), USB connections are directed; a host device has "downstream" facing ports that connect to the "upstream" facing ports of devices. Only downstream facing ports provide power; this topology was chosen to easily prevent electrical overloads and damaged equipment. Thus, USB cables have different ends: A and B, with different physical connectors for each. Each format has a plug and receptacle defined for each of the A and B ends. A USB cable, by definition, has a plug on each end—one A (or C) and one B (or C)—and the corresponding receptacle is usually on a computer or electronic device. The mini and micro formats may connect to an AB receptacle, which accepts either an A or a B plug, that plug determining the behavior of the receptacle.

The three sizes of USB connectors are the default, or ''standard'', format intended for desktop or portable equipment, the ''mini'' intended for mobile equipment, which was deprecated when it was replaced by the thinner ''micro'' size, all of which were deprecated in USB 3.2 in favor of Type-C. There are five speeds for USB data transfer: Low Speed, Full Speed<!-- PLEASE DO NOT CHANGE TO 1.1; FS STARTED IN 1.0 -->, High Speed (from version 2.0 of the specification), [[SuperSpeed]] (from version 3.0), and SuperSpeed+ (from version 3.1). The modes have differing hardware and cabling requirements. USB devices have some choice of implemented modes, and USB version is not a reliable statement of implemented modes. Modes are identified by their names and icons, and the specification suggests that plugs and receptacles be color-coded (SuperSpeed is identified by blue).

=== Connector properties ===
[[File:Male and Female USB Connectors.jpg|thumb|Non-standard USB extension cable, plug on the left, receptacle on the right. (USB does not allow extension cables.<ref name="USB 2.0 6.4.4"/> Non-standard cables may work but cannot be presumed reliable.)]]

The connectors the USB committee specifies support a number of USB's underlying goals, and reflect lessons learned from the many connectors the computer industry has used. The connector mounted on the host or device is called the ''receptacle'', and the connector attached to the cable is called the ''plug''.<ref name="USB_3_0_spec">{{Cite book |title=Universal Serial Bus 3.0 Specification: Revision 1.0 |page=531 |date=June 6, 2011 |url=http://www.usb.org/developers/docs/documents_archive/ |archive-url=https://web.archive.org/web/20131230035108/http://www.usb.org/developers/docs/documents_archive/ |archive-date=December 30, 2013 }}</ref> The official USB specification documents also periodically define the term ''male'' to represent the plug, and ''female'' to represent the receptacle.<ref name="usb-ecn">{{cite web |title=USB 2.0 Specification Engineering Change Notice (ECN) #1: Mini-B connector |via=USB.org |date=October 20, 2000 |url=http://www.usb.org/developers/docs/ecn1.pdf |access-date=April 28, 2019 |archive-url=https://web.archive.org/web/20150412121600/http://www.usb.org/developers/docs/ecn1.pdf |archive-date=April 12, 2015 }}</ref>{{clarify|date=April 2024}}

By design, it is difficult to insert a USB plug into its receptacle incorrectly. The USB specification requires that the cable plug and receptacle be marked so the user can recognize the proper orientation.<ref name="USB_3_0_spec"/> The USB-C plug however is reversible. USB cables and small USB devices are held in place by the gripping force from the receptacle, with no screws, clips, or thumb-turns as other connectors use.

The different A and B plugs prevent accidentally connecting two power sources. However, some of this directed topology is lost with the advent of multi-purpose USB connections (such as [[USB On-The-Go]] in smartphones, and USB-powered Wi-Fi routers), which require A-to-A, B-to-B, and sometimes Y/splitter cables. See the [[#USB On-The-Go connectors|USB On-The-Go connectors]] section below for a more detailed summary description.

There are so-called ''cables'' with A plugs on both ends, which may be valid if the "cable" includes, for example, a USB host-to-host transfer device with two ports.<ref name="cablestogo">{{cite web |title= USB connector guide |url= https://www.cablestogo.com/learning/connector-guides/usb |website=C2G |access-date= December 2, 2013 |url-status= live |archive-url= https://web.archive.org/web/20140421223137/http://www.cablestogo.com/learning/connector-guides/usb |archive-date=April 21, 2014}}</ref> This is, by definition, a device with two logical B ports, each with a captive cable, not a cable with two A ends.

==== Durability ====
The standard connectors were designed to be more robust than many past connectors. This is because USB is [[Hot swapping |hot-swappable]], and the connectors would be used more frequently, and perhaps with less care, than previous connectors.

Standard USB has a minimum rated lifetime of 1,500 cycles of insertion and removal,<ref name="usb.org-cabconn"/> the Mini-USB receptacle increased this to 5,000 cycles,<ref name="usb.org-cabconn"/> and the newer Micro-USB<ref name="usb.org-cabconn">{{cite web |url=http://www.usb.org/developers/devclass_docs/CabConn20.pdf |title=Universal Serial Bus Cables and Connectors Class Document – Revision 2.0 |date=August 2007 |publisher=USB Implementers Forum |archive-url=https://web.archive.org/web/20140611014018/http://www.usb.org/developers/devclass_docs/CabConn20.pdf |archive-date=June 11, 2014}}</ref> and USB-C receptacles are both designed for a minimum rated lifetime of 10,000 cycles of insertion and removal.<ref>{{cite web |author-last=Howse |author-first=Brett |title=USB Type-C Connector Specifications Finalized |url=http://www.anandtech.com/show/8377/usb-typec-connector-specifications-finalized |website=AnandTech |access-date=April 24, 2017 |url-status=live |archive-url=https://web.archive.org/web/20170318004627/http://www.anandtech.com/show/8377/usb-typec-connector-specifications-finalized |archive-date=March 18, 2017}}</ref> To accomplish this, a locking device was added and the leaf-spring was moved from the jack to the plug, so that the most-stressed part is on the cable side of the connection. This change was made so that the connector on the less expensive cable would bear the most [[wear]].<ref name="usb.org-cabconn"/>{{Page needed |date=January 2024}}

In standard USB, the electrical contacts in a USB connector are protected by an adjacent plastic tongue, and the entire connecting assembly is usually protected by an enclosing metal shell.<ref name="usb.org-cabconn"/>

The shell on the plug makes contact with the receptacle before any of the internal pins. The shell is typically grounded, to dissipate static electricity and to shield the wires within the connector.

==== Compatibility ====
The USB standard specifies tolerances for compliant USB connectors to minimize physical incompatibilities in connectors from different vendors. The USB specification also defines limits to the size of a connecting device in the area around its plug, so that adjacent ports are not blocked. Compliant devices must either fit within the size restrictions or support a compliant cable that does.

==== Pinouts ====
{{See also|USB 3.0#PINOUTS|l1=USB 3.0 § Pinouts}}

USB 2.0 uses two wires for power (V<sub>BUS</sub> and GND), and two for [[differential signalling|differential serial data signals]]. Mini and micro connectors have their GND connections moved from pin #4 to pin #5, while their pin #4 serves as an ID pin for the On-The-Go host/client identification.<ref>{{cite web |url=http://www.usbpinout.net/ |title=USB Pinout |website=UsbPinout.net |archive-url=https://web.archive.org/web/20140617072910/http://www.usbpinout.net/ |archive-date=June 17, 2014}}</ref>

USB&nbsp;3.0 provides two additional differential pairs (four wires, SSTx+, SSTx−, SSRx+ and SSRx−), providing [[full-duplex]] data transfers at ''SuperSpeed'', which makes it similar to [[Serial ATA]] or single-lane [[PCI Express]].

[[File:USB 2.0 connectors.svg|thumb|left|'''Standard, Mini-, and Micro-USB plugs''' shown end-on, not to scale. Light areas represent cavities. The plugs are pictured with USB logo to the top.<ref name="microspec" />]]
[[File:USB 3.0 Micro-B plug.png|thumb|'''Micro-B SuperSpeed plug'''
{{ordered list
|1= Power (V<sub>BUS</sub>, 5&nbsp;V)
|2= Data− (D−)
|3= Data+ (D+)
|4= ID (On-The-Go)
|5= GND
|6= SuperSpeed transmit− (SSTx−)
|7= SuperSpeed transmit+ (SSTx+)
|8= GND
|9= SuperSpeed receive− (SSRx−)
|10= SuperSpeed receive+ (SSRx+)
}}]]

{| class="wikitable"
|+ Type-A and -B pinout
|-
! Pin
! Name
! colspan=2 | Wire color{{efn|name="pinout"|In some sources D+ and D− are erroneously swapped.}}
! Description
|-
| 1
| V<sub>BUS</sub>
|style=background:red;color:white| Red or
|style=background:orange;     | Orange
| +5&nbsp;V
|-
| 2
| D−
|style=background:white| White or
|style=background:gold| Gold
| Data−
|-
| 3
| D+
| colspan=2 style=background:green;color:white| Green
| Data+
|-
| 4
| [[Ground (electricity)|GND]]
|style=background:black;color:white| Black or
|style=background:blue;color:white| Blue
| Ground
|}

{| class="wikitable"
|+ Mini/Micro-A and -B pinout
|- style="background:#e0e0e0;"
! Pin
! Name
! Wire color{{efn|name=pinout}}
! Description
|-
| 1
| V<sub>BUS</sub>
|style=background:red;color:white| Red
| +5&nbsp;V
|-
| 2
| D−
|style=background:white| White
| Data−
|-
| 3
| D+
|style=background:green;color:white| Green
| Data+
|-
| 4
| ID
| {{n/a|No wire}}
| [[#USB On-The-Go connectors|On-The-Go]] ID distinguishes cable ends:
* "A" plug (host): connected to GND
* "B" plug (device): not connected
|-
| 5
| GND
|style=background:black;color:white| Black
| Signal ground
|}
{{Notelist|group="pinout"}}

==== Colors ====
[[File:Orange USB port.jpg|thumb|A yellow charge-only "USB" Type-A receptacle and a USB 3.0 Type-A receptacle, both upside-down, on a front panel with card reader]]

[[File:Blue USB port without USB 3.0 contacts.jpg|thumb|A blue Standard-A USB receptacle without USB 3.0 contacts fitted]]

{| class="wikitable"
|+ Usual USB color-coding
|-
! colspan="7" | Color
! Location
! Description
|-
| colspan="3" style="background-color:black; width:5px;" |
| colspan="3" style="background-color:white; width:5px;" |
| Black or white
| Receptacles and plugs
| Type-A or Type-B
|-
| colspan="6" style="background-color:#005eb8; width:5px;" |
| Blue ([[Pantone]] 300C)
| Receptacles and plugs
| Type-A or Type-B, SuperSpeed
|-
| colspan="6" style="background-color:#6cb0c5; width:5px;" |
| Teal blue<!--See [[Teal#Teal blue]].-->
| Receptacles and plugs
| Type-A or Type-B, SuperSpeed+
|-
| colspan="6" style="background-color:#00C000; width:5px;" |
| Green
| Receptacles and plugs
| Type-A or Type-B, [[Qualcomm]] [[Quick Charge|Quick Charge (QC)]]
|-
| colspan="6" style="background-color:#800080; width:5px;" |
| Purple
| Plugs only
| Type-A or Type-C, [[Huawei]] SuperCharge
|-
| colspan="3" style="background-color:yellow; width:5px;" |
| colspan="3" style="background-color:red; width:5px;" |
| Yellow or red
| Receptacles only
| High-current or [[#Sleep-and-charge ports|sleep-and-charge]]
|-
| colspan="6" style="background-color:orange; width:5px;" |
| Orange
| Receptacles only
| High-retention connector, mostly used on industrial hardware
|}

USB ports and connectors are often color-coded to distinguish their different functions and USB versions. These colors are not part of the USB specification and can vary between manufacturers; for example, the USB&nbsp;3.0 specification mandates appropriate color-coding while it only recommends blue inserts for Standard-A USB&nbsp;3.0 connectors and plugs.<ref>{{cite web |url=http://www.usb.org/developers/docs/documents_archive/usb_30_spec_070113.zip |title=Universal Serial Bus Revision 3.0 Specification, Sections 3.1.1.1 and 5.3.1.3 |website=Usb.org |format=ZIP |access-date=April 28, 2019 |archive-url=https://web.archive.org/web/20140519092924/http://www.usb.org/developers/docs/documents_archive/usb_30_spec_070113.zip |archive-date=May 19, 2014}}</ref>

=== Connector types ===
USB connector types multiplied as the specification progressed. The original USB specification detailed standard-A and standard-B plugs and receptacles. The connectors were different so that users could not connect one computer receptacle to another. The data pins in the standard plugs are recessed compared to the power pins so that the device can power up before establishing a data connection. Some devices operate in different modes depending on whether the data connection is made. Charging docks supply power and do not include a host device or data pins, allowing any capable USB device to charge or operate from a standard USB cable. Charging cables provide power connections, but not data. In a charge-only cable, the data wires are shorted at the device end, otherwise, the device may reject the charger as unsuitable.

==== Standard connectors <span class="anchor" id="OVERMOLD-BOOT"></span>====
[[File:USB.svg|thumb|Pin configuration of Type-A and Type-B plugs viewed end-on]]
* The Type-A plug. This plug has an elongated rectangular cross-section, inserts into a Type-A receptacle on a ''downstream port'' on a USB host or hub, and carries both power and data. Captive cables on USB devices such as keyboards or mice terminate with a Type-A plug.
* The Type-B plug: This plug has a near square cross-section with the top exterior corners beveled. As part of a removable cable, it inserts into an ''upstream port'' on a device, such as a printer. On some devices, the Type-B receptacle has no data connections, being used solely for accepting power from the upstream device. This two-connector-type scheme (A/B) prevents a user from accidentally creating a loop.<ref>{{cite journal |author-last=Quinnell |author-first=Richard A. |title=USB: a neat package with a few loose ends |journal=EDN Magazine |publisher=Reed |date=October 24, 1996 |url=http://www.edn.com/design/systems-design/4351549/USB-a-neat-package-with-a-few-loose-end |access-date=February 18, 2013 |url-status=live |archive-url=https://web.archive.org/web/20130523185222/http://www.edn.com/design/systems-design/4351549/USB-a-neat-package-with-a-few-loose-end |archive-date=May 23, 2013}}</ref><ref>{{cite web |title=What is the Difference between USB Type A and USB Type B Plug/Connector? |url=http://digital.ni.com/public.nsf/allkb/0E543C70602423C486256DB8006208DE |url-status=live |archive-url=https://web.archive.org/web/20170207031653/http://digital.ni.com/public.nsf/allkb/0E543C70602423C486256DB8006208DE |archive-date=February 7, 2017}}</ref>

{{Anchor|OVERMOLD-BOOT}}
The maximum allowed cross-section of the ''overmold boot'' (which is part of the connector used for its handling) is {{convert|16|by|8|mm|abbr=on}} for the Standard-A plug type, while for the Type-B it is {{convert|11.5|by|10.5|mm|abbr=on}}.<ref name="usb-ecn"/>

==== Mini connectors <span class="anchor" id="MINI"></span>====
[[File:Mini usb AB.jpg|thumb|Mini-A (left) and Mini-B (right) plugs]]

Mini-USB connectors were introduced together with USB 2.0 in April 2000, mostly used with smaller devices such as [[digital camera]]s, [[smartphone]]s, and [[tablet computer]]s. The Mini-A connector and the Mini-AB receptacle connector have been [[deprecation|deprecated]] since May 2007.<ref name="depmini">{{cite press release |publisher=USB Implementers Forum |title=Deprecation of the Mini-A and Mini-AB Connectors |date=May 27, 2007 |access-date=January 13, 2009 |url=http://www.usb.org/developers/Deprecation_Announcement_052507.pdf |url-status=dead |archive-url=https://web.archive.org/web/20090306145248/http://www.usb.org/developers/Deprecation_Announcement_052507.pdf |archive-date=March 6, 2009}}</ref> Mini-B connectors are still supported, but are not [[On-The-Go]]-compliant;<ref>{{cite web |publisher=USB IF Compliance Updates |title=ID Pin Resistance on Mini B-plugs and Micro B-plugs Increased to 1 Mohm |date=December 2009 |access-date=March 1, 2010 |url=http://compliance.usb.org/index.asp?UpdateFile=Cables%20and%20Connectors&Format=Standard#63 |url-status=live |archive-url=https://web.archive.org/web/20110720073155/http://compliance.usb.org/index.asp?UpdateFile=Cables%20and%20Connectors&Format=Standard#63 |archive-date=July 20, 2011}}</ref> the Mini-B USB connector was standard for transferring data to and from the early smartphones and PDAs. Both Mini-A and Mini-B plugs are approximately {{convert|3|by|7|mm|abbr=on}}. The Mini-AB receptacle accepts either a Mini-A or Mini-B plug.

==== Micro connectors <span class="anchor" id="MICRO"></span>====
{{Multiple image
| total_width=300
| image_gap = 20
| caption_align = center
| image1=A Micro-A USB port.jpeg
| caption1=Micro-A<br />plug
| image2=MicroB USB Plug.jpg
| caption2=Micro-B<br />plug
}}

Micro-USB connectors, which were announced by the [[USB Implementers Forum|USB-IF]] on January 4, 2007,<ref name="CabConn20">{{Citation |title=Universal Serial Bus Cables and Connectors Class Document |date=August 2007 |url=http://www.usb.org/developers/docs/devclass_docs/CabConn20.pdf |archive-url=https://web.archive.org/web/20150427001335/http://www.usb.org/developers/docs/devclass_docs/CabConn20.pdf |url-status=live |version=Revision 2.0 |page=6 |publisher=USB Implementers Forum |access-date=August 17, 2014 |archive-date=April 27, 2015}}</ref><ref>{{cite press release |publisher=USB Implementers Forum |title=Mobile phones to adopt new, smaller USB connector |date=January 4, 2007 |access-date=January 8, 2007 |url=http://www.usb.org/press/pressroom/2007_01_04_usbif.pdf |url-status=live |archive-url=https://web.archive.org/web/20070108050844/http://www.usb.org/press/pressroom/2007_01_04_usbif.pdf |archive-date=January 8, 2007}}</ref> have a similar width to Mini-USB, but approximately half the thickness, enabling their integration into thinner portable devices. The Micro-A connector is {{convert|6.85|by|1.8|mm|abbr=on}} with a maximum overmold boot size of {{convert|11.7|by|8.5|mm|abbr=on}}, while the Micro-B connector is {{convert|6.85|by|1.8|mm|abbr=on}} with a maximum overmold size of {{convert|10.6|by|8.5|mm|abbr=on}}.<ref name="microspec">{{cite web |url=http://mgvs.org/public/shema/datasheet/usb_20/Micro-USB_final/Micro-USB_1_01.pdf |title=Universal Serial Bus Micro-USB Cables and Connectors Specification |date=April 4, 2007 |publisher=USB Implementers Forum|url-status=live |archive-url=https://web.archive.org/web/20151115224048/http://mgvs.org/public/shema/datasheet/usb_20/Micro-USB_final/Micro-USB_1_01.pdf |archive-date=November 15, 2015 |access-date=January 31, 2015}}</ref>

The thinner Micro-USB connectors were intended to replace the Mini connectors in devices manufactured since May 2007, including [[smartphone]]s, [[personal digital assistant]]s, and cameras.<ref name="pinoutguide.com 2012">{{cite web |title=Micro-USB mobile phone/smartphone cable connector pinout diagram |website=pinoutguide.com |date=November 16, 2012 |url=https://pinoutguide.com/CellularPhones-A-N/smartphone_microusb_connector_pinout.shtml |archive-url=https://web.archive.org/web/20240527113809/https://pinoutguide.com/CellularPhones-A-N/smartphone_microusb_connector_pinout.shtml |archive-date=May 27, 2024 |url-status=live |access-date=May 29, 2024}}</ref>

The Micro plug design is rated for at least 10,000 connect-disconnect cycles, which is more than the Mini plug design.<ref name="CabConn20" /><ref name="MicroUSB 1.01">{{cite web |url=http://www.usb.org/developers/docs/usb_20_101111.zip |title=Universal Serial Bus Micro-USB Cables and Connectors Specification to the USB 2.0 Specification, Revision 1.01 |date=April 7, 2007 |access-date=November 18, 2010 |publisher=USB Implementers Forum |format=ZIP |quote=Section 1.3: Additional requirements for a more rugged connector that is durable past 10,000 cycles and still meets the USB 2.0 specification for mechanical and electrical performance was also a consideration. The Mini-USB could not be modified and remain backward compatible to the existing connector as defined in the USB OTG specification. |archive-url=https://web.archive.org/web/20120207112406/http://www.usb.org/developers/docs/usb_20_101111.zip |archive-date=February 7, 2012}}</ref> The Micro connector is also designed to reduce the mechanical wear on the device; instead, the easier-to-replace cable is designed to bear the mechanical wear of connection and disconnection. The ''Universal Serial Bus Micro-USB Cables and Connectors Specification'' details the mechanical characteristics of Micro-A [[Electrical connector|plugs]], Micro-AB receptacles (which accept both Micro-A and Micro-B plugs), Double-Sided Micro USB, and Micro-B plugs and receptacles,<ref name="MicroUSB 1.01"/> along with a Standard-A receptacle to a Micro-A plug adapter.

=====OMTP standard=====
Micro-USB was endorsed as the standard connector for data and power on mobile devices by the cellular phone carrier group [[Open Mobile Terminal Platform]] (OMTP) in 2007.<ref>{{cite web |url=http://www.omtp.org/Publications/Display.aspx?Id=08d2e4e3-ebee-407c-a51b-94057e7f7b19 |title=OMTP Local Connectivity: Data Connectivity |publisher=[[Open Mobile Terminal Platform]] |date=September 17, 2007 |access-date=February 11, 2009 |archive-url=https://web.archive.org/web/20081015035350/http://www.omtp.org/Publications/Display.aspx?Id=08d2e4e3-ebee-407c-a51b-94057e7f7b19 |archive-date=October 15, 2008}}</ref>

Micro-USB was embraced as the "Universal Charging Solution" by the [[International Telecommunication Union]] (ITU) in October 2009.<ref>{{cite web |publisher=Pressinfo |url=http://www.itu.int/newsroom/press_releases/2009/49.html |type=press release |title=Universal phone charger standard approved—One-size-fits-all solution will dramatically cut waste and GHG emissions |work=ITU |date=October 22, 2009 |access-date=November 4, 2009 |url-status=live |archive-url=https://web.archive.org/web/20091105075233/http://www.itu.int/newsroom/press_releases/2009/49.html |archive-date=November 5, 2009}}</ref>

In Europe, micro-USB became the defined [[common external power supply]] (EPS) for use with smartphones sold in the EU,<ref>{{cite web |url=http://europa.eu/rapid/pressReleasesAction.do?reference=IP/10/1776&format=HTML&aged=0&language=EN&guiLanguage=en |title=Commission welcomes new EU standards for common mobile phone charger |work=Press Releases |publisher=Europa |date=December 29, 2010 |access-date=May 22, 2011 |url-status=live |archive-url=https://web.archive.org/web/20110319015833/http://europa.eu/rapid/pressReleasesAction.do?reference=IP%2F10%2F1776&format=HTML&aged=0&language=EN&guiLanguage=en |archive-date=March 19, 2011}}</ref> and 14 of the world's largest mobile phone manufacturers signed the EU's common EPS Memorandum of Understanding (MoU).<ref>{{citation | url = http://europa.eu/rapid/pressReleasesAction.do?reference=IP/10/1776 | title = New EU standards for common mobile phone charger | publisher = Europa | type = press release | url-status = live | archive-url = https://web.archive.org/web/20110103181049/http://europa.eu/rapid/pressReleasesAction.do?reference=IP%2F10%2F1776 | archive-date = January 3, 2011 }}</ref><ref>{{citation | url = http://europa.eu/rapid/pressReleasesAction.do?reference=MEMO/09/301 | archive-url = https://web.archive.org/web/20090704130734/http://europa.eu/rapid/pressReleasesAction.do?reference=MEMO%2F09%2F301 | url-status = live | archive-date = July 4, 2009 | title = The following 10 biggest mobile phone companies have signed the MoU: Apple, LG, Motorola, NEC, Nokia, Qualcomm, Research In Motion, Samsung, Sony Ericsson, Texas Instruments | publisher = Europa | type = press release }}</ref> [[Apple Inc.|Apple]], one of the original MoU signers, makes Micro-USB adapters available—as permitted in the Common EPS MoU—for its [[iPhone]]s equipped with Apple's proprietary [[Dock connector#Mobile devices|30-pin dock connector]] or (later) [[Lightning (connector)|Lightning connector]].<ref>{{cite news |url=http://gigaom.com/apple/nice-micro-usb-adapter-apple-now-sell-it-everywhere/ |title=Nice Micro-USB Adapter Apple, Now Sell It Everywhere |date=October 5, 2011 |newspaper=Giga om |url-status=live |archive-url=https://web.archive.org/web/20120826101535/http://gigaom.com/apple/nice-micro-usb-adapter-apple-now-sell-it-everywhere/ |archive-date=August 26, 2012}}</ref><ref>{{Citation |url=https://www.engadget.com/2012/11/03/apples-lightning-to-microusb-adapter-in-us/ |title=Apple's Lightning to Micro-USB adapter now available in US, not just Europe anymore |date=November 3, 2012 |newspaper=Engadget |url-status=live |archive-url=https://web.archive.org/web/20170626193154/https://www.engadget.com/2012/11/03/apples-lightning-to-microusb-adapter-in-us/ |archive-date=June 26, 2017}}</ref> according to the [[European Committee for Standardization|CEN]], [[European Committee for Electrotechnical Standardization|CENELEC]], and [[ETSI]].

==== USB 3.''x'' connectors and backward compatibility ====
[[File:Connector USB 3 IMGP6033 wp.jpg|thumb|right|USB 3.0 Micro-B SuperSpeed plug]]
{{See also|USB 3.0#CONNECTORS|l1=USB 3.0 § Connectors}}

USB 3.0 introduced Type-A SuperSpeed plugs and receptacles as well as micro-sized Type-B SuperSpeed plugs and receptacles. The 3.0 receptacles are backward-compatible with the corresponding pre-3.0 plugs.

USB 3.''x'' and USB 1.''x'' Type-A plugs and receptacles are designed to interoperate. To achieve USB&nbsp;3.0's SuperSpeed (and SuperSpeed+ for USB&nbsp;3.1&nbsp;Gen&nbsp;2), 5 extra pins are added to the unused area of the original 4 pin USB&nbsp;1.0 design, making USB&nbsp;3.0 Type-A plugs and receptacles backward compatible to those of USB&nbsp;1.0.

On the device side, a modified Micro-B plug (Micro-B SuperSpeed) is used to cater for the five additional pins required to achieve the USB 3.0 features (USB-C plug can also be used). The USB 3.0 Micro-B plug effectively consists of a standard USB 2.0 Micro-B cable plug, with an additional 5 pins plug "stacked" to the side of it. In this way, cables with smaller 5 pin USB 2.0 Micro-B plugs can be plugged into devices with 10 contact USB 3.0 Micro-B receptacles and achieve backward compatibility.

USB cables exist with various combinations of plugs on each end of the cable, as displayed below in the ''USB cables matrix''.

[[File:USB-3.0-Typ-B-Stecker -- 2014 -- 1709.jpg|alt=USB 3.0 Type-B plug|thumb|USB 3.0 Standard-B plug]]

==== USB On-The-Go connectors ====
{{Main|USB On-The-Go}}
[[USB On-The-Go]] (OTG) introduces the concept of a device performing both host and device roles. All current OTG devices are required to have one, and only one, USB connector: a Micro-AB receptacle. (In the past, before the development of Micro-USB, On-The-Go devices used ''Mini''-AB receptacles.)

The Micro-AB receptacle is capable of accepting Micro-A and Micro-B plugs, attached to any of the legal cables and adapters as defined in revision 1.01 of the Micro-USB specification.

To enable Type-AB receptacles to distinguish which end of a cable is plugged in, plugs have an "ID" pin in addition to the four contacts in standard-size USB connectors. This ID pin is connected to GND in Type-A plugs, and left unconnected in Type-B plugs. Typically, a [[pull-up resistor]] in the device is used to detect the presence or absence of an ID connection.

The OTG device with the A-plug inserted is called the A-device and is responsible for powering the USB interface when required, and by default assumes the role of host. The OTG device with the B-plug inserted is called the B-device and by default assumes the role of peripheral. An OTG device with no plug inserted defaults to acting as a B-device. If an application on the B-device requires the role of host, then the Host Negotiation Protocol (HNP) is used to temporarily transfer the host role to the B-device.

OTG devices attached either to a peripheral-only B-device or a standard/embedded host have their role fixed by the cable, since in these scenarios it is only possible to attach the cable one way.{{Citation needed|date=October 2011}}

==== USB-C <span class="anchor" id="TYPE-C"></span>====
{{Main|USB-C}}
[[File:USB Type-C icon.svg|thumb|The [[USB-C]] plug]]
[[File:USB Type-C macbook.png|thumb|USB cable with a USB-C plug and a USB-C port on a notebook computer]]

The USB-C connector supersedes all earlier USB connectors and the Mini DisplayPort connector. It is used for all USB protocols and for Thunderbolt (3 and later), DisplayPort (1.2 and later), and others. Developed at roughly the same time as the USB&nbsp;3.1 specification, but distinct from it, the USB-C Specification 1.0 was finalized in August 2014<ref name="Cfinalized" /> and defines a new small reversible-plug connector for USB devices.<ref name="difference">{{cite web |url=http://www.extremetech.com/computing/197145-reversible-usb-type-c-finally-on-its-way-alongside-usb-3-1s-10gbit-performance |title=USB-C vs. USB 3.1: What's the difference? |website=ExtremeTech |date=March 13, 2015 |access-date=April 9, 2015 |author-last=Hruska |author-first=Joel |url-status=live |archive-url=https://web.archive.org/web/20150411081838/http://www.extremetech.com/computing/197145-reversible-usb-type-c-finally-on-its-way-alongside-usb-3-1s-10gbit-performance |archive-date=April 11, 2015}}</ref> The USB-C plug connects to both hosts and devices, replacing various Type-A and Type-B connectors and cables with a standard meant to be [[future-proof]].<ref name="Cfinalized">{{cite web |title=USB Type-C Connector Specifications Finalized |url=http://www.anandtech.com/show/8377/usb-typec-connector-specifications-finalized |author-last=Howse |author-first=Brett |date=August 12, 2014 |access-date=December 28, 2014 |url-status=live |archive-url=https://web.archive.org/web/20141228122529/http://www.anandtech.com/show/8377/usb-typec-connector-specifications-finalized |archive-date=December 28, 2014}}</ref><ref name="ngo2014">{{cite web |author-last=Ngo |author-first=Dong |title=USB Type-C: One Cable to Connect Them All|url= https://www.cnet.com/news/usb-type-c-one-cable-to-connect-them-all/ |date=August 22, 2014 |website=c.net |access-date=December 28, 2014 |archive-url=https://web.archive.org/web/20150307064003/http://www.cnet.com/news/usb-type-c-one-cable-to-connect-them-all |archive-date=March 7, 2015}}</ref>

The 24-pin double-sided connector provides four power–ground pairs, two differential pairs for USB&nbsp;2.0 data (though only one pair is implemented in a USB-C cable), four pairs for SuperSpeed data bus (only two pairs are used in USB 3.1 mode), two "sideband use" pins, V<sub>CONN</sub> +5&nbsp;V power for active cables, and a configuration pin for cable orientation detection and dedicated [[biphase mark code]] (BMC) configuration data channel (CC).<ref name="IDF14-TypeC">{{cite web |url=https://intel.activeevents.com/sf14/connect/sessionDetail.ww?SESSION_ID=1254 |title=Technical Introduction of the New USB Type-C Connector |access-date=December 29, 2014 |archive-url=https://web.archive.org/web/20141229123208/https://intel.activeevents.com/sf14/connect/sessionDetail.ww?SESSION_ID=1254 |archive-date=December 29, 2014}}</ref><ref name="TypeC-DP1.3">{{cite web |title=DisplayPort Alternate Mode for USB Type-C Announced - Video, Power, & Data All Over Type-C |url=http://www.anandtech.com/show/8558/displayport-alternate-mode-for-usb-typec-announced |author-last=Smith |author-first=Ryan |date=September 22, 2014 |website=[[AnandTech]] |access-date=December 28, 2014 |url-status=live |archive-url=https://web.archive.org/web/20141218171152/http://www.anandtech.com/show/8558/displayport-alternate-mode-for-usb-typec-announced |archive-date=December 18, 2014}}</ref> Type-A and Type-B adaptors and cables are required for older hosts and devices to plug into USB-C hosts and devices. Adapters and cables with a USB-C receptacle are not allowed.<ref>''Universal Serial Bus Type-C Cable and Connector Specification'' Revision 1.1 (April 3, 2015), section 2.2, page 20</ref>

{{anchor|E-Mark}}Full-featured USB-C 3.1 cables contain a full set of wires and are "electronically marked" ([[E-marked USB cable|E-marked]]): they contain a "eMarker" chip that responds to the [[#USB Power Delivery|USB Power Delivery]] ''Discover Identity'' command, a kind of vendor-defined message (VDM) sent over the configuration data channel (CC). Using this command, the cable reports its current capacities, maximum speed, and other parameters.<ref name="USBC22">{{cite tech report |url=https://www.usb.org/document-library/usb-type-cr-cable-and-connector-specification-release-22 |title=Universal Serial Bus Type-C Cable and Connector Specification, Release 2.2 |work=USB Implementers Forum |date=October 2022 |institution=USB 3.0 Promoter Group |access-date=April 12, 2023}}</ref>{{rp|at=&sect;4.9}} Full-Featured USB Type-C devices are a mechanic prerequisite for multi-lane operation (USB 3.2 Gen 1x2, USB 3.2 Gen 2x2, USB4 2x2, USB4 3x2, USB Gen 4 Asymmetric).<ref name="USBC22"/>

USB-C devices support power currents of 1.5&nbsp;A and 3.0&nbsp;A over the 5&nbsp;V power bus in addition to baseline 900&nbsp;mA. These higher currents can be negotiated through the configuration line. Devices can also utilize the full Power Delivery specification using both BMC-coded configuration line and legacy [[frequency-shift keying|BFSK]]-coded V<sub>BUS</sub> line.<ref name="USBC22"/>{{rp|at=&sect;4.6.2.1}}

==== Host and device interface receptacles ====
USB plugs fit one receptacle with notable exceptions for USB On-The-Go "AB" support and the general backward compatibility of USB&nbsp;3.0 as shown.

{| class="wikitable"
|+ USB connector mating table (images not to scale)
|-
! {{diagonal split header|Receptacle|Plug}}
! USB A<br />[[File:USB Type-A.svg|75px]]
! USB 3.0 A SS<br />[[File:USB 3.0 Type-A blue.svg|85px]]
! USB B<br />[[File:USB Type-B.svg|x70px]]
! USB 3.0 B SS<br />[[File:USB 3.0 Type-B blue.svg|65px]]
! USB Mini-A<br />[[File:USB Mini-A.svg|75px]]
! USB Mini-B<br />[[File:USB Mini-B.svg|75px]]
! USB Micro-A{{ref|Micro-A Receptacle|1}}<br />[[File:USB Micro-A.svg|75px]]
! USB Micro-B<br />[[File:USB Micro-B.svg|x50px]]
! USB 3.0 Micro-B<br />[[File:USB 3.0 Micro-B.svg|120px]]
! USB-C[[File:USB Type-C plug pinout.svg|center|frameless|60x60px]]
|-
! USB A<br />[[File:USB Type-A receptacle.svg|75px]]
| {{Yes}}
| {{Yes|Only non-<br />SuperSpeed}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
|-
! USB 3.0 A SS<br />[[File:USB 3.0 Type-A receptacle blue.svg|75px]]
| {{Yes|Only non-<br />SuperSpeed}}
| {{Yes}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
|-
! USB B<br />[[File:USB Type-B receptacle.svg|x60px]]
| {{No}}
| {{No}}
| {{Yes}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
|-
! USB 3.0 B SS<br />[[File:USB 3.0 Type-B receptacle blue.svg|60px]]
| {{No}}
| {{No}}
| {{Yes|Only non-<br />SuperSpeed}}
| {{Yes}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
|-
! USB Mini-A<br />[[File:USB Mini-A receptacle.svg|60px]]
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{Yes}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
|-
! USB Mini-AB<br />[[File:USB Mini-AB receptacle.svg|60px]]
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{Depends|Deprecated}}
| {{Depends|Deprecated}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
|-
! USB Mini-B<br />[[File:USB Mini-B receptacle.svg|60px]]
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{Yes}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
|-
! USB Micro-AB<br />[[File:USB Micro-AB receptacle.svg|60px]]
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{Yes}}
| {{Yes}}
| {{No}}
| {{No}}
|-
! USB Micro-B<br />[[File:USB Micro-B receptacle.svg|60px]]
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{Yes}}
| {{No}}
| {{No}}
|-
! USB 3.0 Micro-B SS<br />[[File:USB 3.0 Micro-B receptacle.svg|100px]]
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{Yes|Only non-<br />SuperSpeed}}
| {{Yes}}
| {{No}}
|-
! USB-C[[File:USB Type-C Receptacle Pinout.svg|center|frameless|60x60px]]
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{Yes}}
|-
| colspan="11" | {{note|Micro-A Receptacle|1}} <small>No corresponding Micro-A receptacle was ever designed.</small>
|}

{| class="wikitable"
|+ USB cables table
|-
! Plugs, each end
! USB A<br />[[File:USB Type-A.svg|x55px]]
! USB Mini-A<br />[[File:USB Mini-A.svg|x60px]]
! USB Micro-A<br />[[File:USB Micro-A.svg|x60px]]
! USB B<br />[[File:USB Type-B.svg|x70px]]
! USB Mini-B<br />[[File:USB Mini-B.svg|x60px]]
! USB Micro-B<br />[[File:USB Micro-B.svg|x60px]]
! USB 3.0 Micro-B<br />[[File:USB 3.0 Micro-B.svg|120px]]
! USB-C[[File:USB Type-C plug pinout.svg|center|frameless|60x60px]]
|-
! USB A<br />[[File:USB Type-A.svg|x55px]]
| {{No2|Proprietary,<br/>hazardous}}<ref name="USB 2.0 6.4.4"/> <!-- DO NOT CHANGE THIS AGAIN TO YES. AN A-TO-A CABLE IS REALLY NON-STANDARD AND EVEN DANGEROUS TO USE. -->
| {{No2|Proprietary,<br/>hazardous}}<ref name="USB 2.0 6.4.4"/>
| {{No2|Proprietary,<br/>hazardous}}<ref name="USB 2.0 6.4.4"/>
| {{Yes}}
| {{Yes}}
| {{Yes}}
| {{Yes}}
| {{Yes}}
|-
! USB Mini-A<br/>[[File:USB Mini-A.svg|x60px]]
| {{No2|Proprietary,<br/>hazardous}}<ref name="USB 2.0 6.4.4"/>
| {{No}}
| {{No}}
| {{Depends|Deprecated}}
| {{Depends|Deprecated}}
| {{Yes2|Non-<br/>standard}}
| {{No}}
| {{No}}
|-
! USB Micro-A<br />[[File:USB Micro-A.svg|x60px]]
| {{No2|Proprietary,<br />hazardous}}<ref name="USB 2.0 6.4.4"/>
| {{No}}
| {{No}}
| {{Yes2|Non-<br />standard}}
| {{Yes2|Non-<br />standard}}
| {{Yes}}
| {{No}}
| {{No}}
|-
! USB B<br />[[File:USB Type-B.svg|x70px]]
| {{Yes}}
| {{Depends|Deprecated}}
| {{Yes2|Non-<br />standard}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{Yes}}
|-
! USB Mini-B<br />[[File:USB Mini-B.svg|x60px]]
| {{Yes}}
| {{Depends|Deprecated}}
| {{Yes2|Non-<br />standard}}
| {{No}}
| {{unofficial2|OTG non-<br />standard}}
| {{unofficial2|OTG non-<br />standard}}
| {{No}}
| {{Yes}}
|-
! USB Micro-B<br />[[File:USB Micro-B.svg|x60px]]
| {{Yes}}
| {{Yes2|Non-<br />standard}}
| {{Yes}}
| {{No}}
| {{unofficial2|OTG non-<br />standard}}
| {{unofficial2|OTG non-<br />standard}}
| {{No}}
| {{Yes}}
|-
! USB 3.0 Micro-B<br />[[File:USB 3.0 Micro-B.svg|120px]]
| {{Yes}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{No}}
| {{unofficial2|OTG non-<br />standard}}
| {{Yes}}
|-
! USB-C[[File:USB Type-C plug pinout.svg|center|frameless|60x60px]]
| {{Yes}}
| {{No}}
| {{No}}
| {{Yes}}
| {{Yes}}
| {{Yes}}
| {{Yes}}
| {{Yes}}
|}

;{{color box|#fdd}} Proprietary, hazardous: Existing for specific [[Proprietary hardware|proprietary purposes]], not inter-operable with USB-IF compliant equipment and possibly damaging to both devices when plugged in. In addition to the above cable assemblies comprising two plugs, an "adapter" cable with a Micro-A plug and a standard-A receptacle is compliant with USB specifications.<ref name="microspec"/> Other combinations of connectors are not compliant.{{paragraph break}}There do exist A-to-A assemblies, referred to as cables (such as the [[Easy Transfer Cable]]); however, these have a pair of USB devices in the middle, making them more than just cables.
;{{color box|#bfd}} Non-standard: The USB standards do not exhaustively list all combinations with one Type-A and one Type-B connector, however, most such cables have good chances of working.
;{{color box|#afe}} OTG non-standard: Commonly available "OTG" cables that address widespread misuse of Micro-B and Mini-B receptacles for OTG devices, e.g. smartphones (as opposed to Micro-AB and Mini-AB, which accept either plug.) While not compliant with the USB standards, these cables at least do not provide a device damage hazard since Type-B ports on devices are unpowered by default.<ref>{{cite web |url=https://www.usb.org/sites/default/files/documents/usb_otg_and_eh_3-0_release_1_1_10may2012.pdf |title=On-The-Go and Embedded Host Supplement to the USB Revision 3.0 Specification |version=Revision 1.1 |date=May 10, 2012 |website=USB.org}}</ref>
;{{color box|#fed}} [[Deprecation|Deprecated]]: Some older devices and cables with Mini-A connectors have been certified by USB-IF. The Mini-A connector is obsolete: no new Mini-A connectors and neither Mini-A nor Mini-AB receptacles will be certified.<ref name="depmini"/>{{paragraph break}}Note: Mini-B is not deprecated, although it is less and less used since the arrival of Micro-B. Micro-A and Micro-B have one more contact than Standard-A and Standard-B in order for hardware with a Micro-AB receptacle to discern Micro-A from Micro-B and behave as a host or device accordingly.

===Proprietary connectors and formats===
Manufacturers of personal electronic devices might not include a USB standard connector on their product for technical or marketing reasons.<ref>{{cite web |url=http://anythingbutipod.com/2008/04/proprietary-cable-vs-standard-usb/ |title=Proprietary Cables vs Standard USB |date=April 30, 2008 |access-date=October 29, 2013 |website=anythingbutipod.com |archive-url=https://web.archive.org/web/20131113215722/http://anythingbutipod.com/2008/04/proprietary-cable-vs-standard-usb/ |archive-date=November 13, 2013}}</ref> E.g. Olympus has been using a special cable called CB-USB8 one end of which has a special contact. Some manufacturers provide proprietary cables, such as [[Lightning (connector)|Lightning]], that permit their devices to physically connect to a USB standard port. Full functionality of proprietary ports and cables with USB standard ports is not assured; for example, some devices only use the USB connection for battery charging and do not implement any data transfer functions.<ref>{{cite web |url=http://www.macworld.com/article/2028888/review-logitechs-ultrathin-mini-keyboard-cover-makes-the-wrong-tradeoffs.html |title=Review: Logitech's Ultrathin mini keyboard cover makes the wrong tradeoffs |date=February 25, 2013 |access-date=October 29, 2013 |author-first=Lex |author-last=Friedman |website=macworld.com |url-status=live |archive-url=https://web.archive.org/web/20131103072153/http://www.macworld.com/article/2028888/review-logitechs-ultrathin-mini-keyboard-cover-makes-the-wrong-tradeoffs.html |archive-date=November 3, 2013}}</ref>

== Cabling <span class="anchor" id="CABLING"></span>==
[[File:USB Twisted Pair.svg|thumb|upright=1.2|A USB twisted pair, in which the ''Data+'' and ''Data−'' conductors are twisted together in a double [[helix]]. The wires are enclosed in a further layer of shielding.]]

The D± signals used by low, full, and high speed are carried over a [[twisted pair]] (typically unshielded) to reduce [[signal noise|noise]] and [[crosstalk (electronics)|crosstalk]]. SuperSpeed uses separate transmit and receive [[Differential signaling|differential pair]]s, which additionally require shielding (typically, shielded twisted pair but [[twinax]] is also mentioned by the specification). Thus, to support SuperSpeed data transmission, cables contain twice as many wires and are larger in diameter.<ref>{{cite web |url=http://hantat.com/News-Read-459-1.html |title=What Is the USB 3.0 Cable Difference |publisher=Hantat |date=May 18, 2009 |archive-url=https://web.archive.org/web/20111211232404/http://hantat.com/News-Read-459-1.html |archive-date=December 11, 2011 |access-date=December 12, 2011}}</ref>

The USB&nbsp;1.1 standard specifies that a standard cable can have a maximum length of {{convert|5|m|ftin}} with devices operating at full speed (12&nbsp;Mbit/s), and a maximum length of {{convert|3|m|ftin}} with devices operating at low speed (1.5&nbsp;Mbit/s).<ref>{{cite web |url=http://www.cablesplususa.com/pdf/USB_Cable_Length_Limitations.pdf |title=USB Cable Length Limitations |website=cablesplususa.com |date=November 3, 2010 |archive-url=https://web.archive.org/web/20141011015850/http://www.cablesplususa.com/pdf/USB_Cable_Length_Limitations.pdf |archive-date=October 11, 2014 |access-date=February 2, 2014}}</ref><ref>{{cite web |url=https://www.techwalla.com/articles/what-is-the-maximum-length-of-a-usb-cable |title=What is the Maximum Length of a USB Cable? |website=Techwalla.com |url-status=live |archive-url=https://web.archive.org/web/20171201043247/https://www.techwalla.com/articles/what-is-the-maximum-length-of-a-usb-cable |archive-date=December 1, 2017 |access-date=November 18, 2017}}</ref><ref name="faq">{{cite web |url=http://www.usb.org/developers/usbfaq#cab1 |title=USB Frequently Asked Questions: Cables and Long-Haul Solutions |website=USB.org |archive-url=https://web.archive.org/web/20140115191641/http://www.usb.org/developers/usbfaq/#cab1 |archive-date=January 15, 2014 |access-date=May 22, 2023}}</ref>

USB&nbsp;2.0 provides for a maximum cable length of {{convert|5|m|ftin}} for devices running at high speed (480&nbsp;Mbit/s). The primary reason for this limit is the maximum allowed round-trip delay of about 1.5&nbsp;μs. If USB host commands are unanswered by the USB device within the allowed time, the host considers the command lost. When adding USB device response time, delays from the maximum number of hubs added to the delays from connecting cables, the maximum acceptable delay per cable amounts to 26&nbsp;ns.<ref name="faq" /> The USB&nbsp;2.0 specification requires that cable delay be less than {{nowrap|5.2&nbsp;ns/m}} ({{nowrap|1.6&nbsp;ns/ft}}, {{nowrap|{{gaps|192|000}} km/s}}), which is close to the maximum achievable transmission speed for standard copper wire.

The USB&nbsp;3.0 standard does not directly specify a maximum cable length, requiring only that all cables meet an electrical specification: for copper cabling with [[American wire gauge|AWG]]&nbsp;26 wires the maximum practical length is {{convert|3|m|ftin}}.<ref>{{cite web |title=USB 3.0 Developers FAQ |url=http://janaxelson.com/usb3faq.htm#ca_maximum |author-last=Axelson |author-first=Jan |url-status=live |archive-url=https://web.archive.org/web/20161220073858/http://www.janaxelson.com/usb3faq.htm#ca_maximum |archive-date=December 20, 2016 |access-date=October 20, 2016}}</ref>

== Power <span class="anchor" id="POWER"></span>==
{{See also|USB hub#Power}}

Downstream USB connectors supply power at a nominal {{nowrap|5 V DC}} via the V_BUS pin to upstream USB devices.

=== Voltage tolerance and limits ===
[[File:USB Specification 2.0 Figure 7-47 - Worst-case Voltage Drop Topology (Steady State).png|thumb|upright=1.2|Worst-case voltage drop topology of a USB 2.0 host to low-power device chain, at steady state]]

The tolerance on V_BUS at an upstream (or host) connector was originally ±5% (i.e. could lie anywhere in the range 4.75&nbsp;V to 5.25&nbsp;V). With the release of the [[USB-C|USB Type-C]] specification in 2014 and its 3&nbsp;A power capability, the [[USB Implementers Forum|USB-IF]] elected to increase the upper voltage limit to 5.5&nbsp;V to combat [[voltage droop]] at higher currents.<ref>{{Cite web |date=March 1, 2021 |title=USB Type-C Revision 1.0 |url=https://www.those.ch/designtechnik/wp-content/uploads/2014/08/USB-Type-C-Specification-Release-1.0.pdf |url-status=live |archive-url=https://web.archive.org/web/20211103140823/https://www.those.ch/designtechnik/wp-content/uploads/2014/08/USB-Type-C-Specification-Release-1.0.pdf |archive-date=November 3, 2021 |access-date=November 3, 2021 |website=USB 3.0 Promoter Group}}</ref> The USB 2.0 specification (and therefore implicitly also the USB 3.''x'' specifications) was also updated to reflect this change at that time.<ref>{{cite web |date=November 3, 2021 |title=USB ECN USB 2.0 VBUS Max Limit |url=https://usb.org/document-library/usb-20-specification |url-status=live |archive-url=https://web.archive.org/web/20211103142016/https://www.usb.org/sites/default/files/usb_20_20211008.zip |archive-date=November 3, 2021 |access-date=November 3, 2021 |website=USB-IF}}</ref> A number of extensions to the USB Specifications have progressively further increased the maximum allowable V_BUS voltage: starting with 6.0&nbsp;V with USB BC 1.2,<ref>{{cite web |date=March 15, 2015 |title=Battery Charging v1.2 Spec and Adopters Agreement |url=https://www.usb.org/sites/default/files/BCv1.2_070312_0.zip |url-status=live |archive-url=https://web.archive.org/web/20211103145550/https://www.usb.org/sites/default/files/BCv1.2_070312_0.zip |archive-date=November 3, 2021 |archive-format=PDF (Zipped) |access-date=November 3, 2021 |website=USB.org |at=Table 5-1 Voltages |format=PDF (Zipped)}}</ref> to 21.5&nbsp;V with USB PD 2.0<ref name=":0">{{cite web |date=October 26, 2021 |title=USB Power Delivery Specifications 2.0 and 3. |url=https://www.usb.org/sites/default/files/USB%20Power%20Delivery%2020211026.zip |url-status=live |archive-url=https://web.archive.org/web/20211103143611/https://www.usb.org/sites/default/files/USB%20Power%20Delivery%2020211026.zip |archive-date=November 3, 2021 |archive-format=PDF (Zipped) |access-date=November 3, 2021 |website=USB.org |format=PDF (Zipped)}}</ref> and 50.9&nbsp;V with USB PD 3.1,<ref name=":0" /> while still maintaining backwards compatibility with USB 2.0 by requiring various forms of [[Handshake (computing)|handshake]] before increasing the nominal voltage above 5&nbsp;V.

USB PD continues the use of the bilateral 5% tolerance, with allowable voltages of {{Abbr|PDO|Power Data Object

Data Object used to expose a Source Port's power capabilities or a Sink's power requirements as part of a Source_Capabilities or Sink_Capabilities Message respectively.

Fixed, Variable and Battery Power Data Objects are defined.}} ±5% ±0.5&nbsp;V (eg. for a PDO of 9.0&nbsp;V, the maximum and minimum limits are 9.95&nbsp;V and 8.05&nbsp;V, respectively).<ref name=":0"/>

There are several minimum allowable voltages defined at different locations within a chain of connectors, hubs, and cables between an upstream host (providing the power) and a downstream device (consuming the power). To allow for voltage drops, the voltage at the host port, hub port, and device are specified to be at least 4.75&nbsp;V, 4.4&nbsp;V, and 4.35&nbsp;V respectively by USB&nbsp;2.0 for low-power devices,{{Efn|Low-power devices are those which draw less than 1 unit load. 1 unit load is 100&nbsp;mA for USB 2.0 |name="low-power USB 2" |group="Power"}} but must be at least 4.75&nbsp;V at all locations for high-power{{Efn|High-power devices in USB 2.0 are those that draw more than one unit load (up to a maximum of 5 unit loads). 1 unit load is 100&nbsp;mA. |name="High-power USB 2" |group="Power"}} devices (however, high-power devices are required to operate as a low-powered device so that they may be detected and enumerated if connected to a low-power upstream port). The USB&nbsp;3.''x'' specifications require that all devices must operate down to 4.00&nbsp;V at the device port.

Unlike USB 2.0 and USB 3.2, USB4 does not define its own VBUS-based power model. Power for USB4 operation is established and managed as defined in the USB Type-C Specification and the USB PD Specification.
{{Notelist|group="Power"}}

[[File:USB Specification 3.0 Figure 11-5 - Worst-case Voltage Drop Topology (Steady State).png|thumb|upright=1.2|Worst-case voltage drop topology of a USB 3.''x'' host to device chain, at steady state. Note that under transient conditions the supply at the device can momentarily drop from 4.0&nbsp;V to 3.67&nbsp;V.]]

=== Allowable current draw ===
{| class="wikitable floatright"
|+ USB power standards
|-
! Specification
! Current
! Voltage
! Power (max.)
|-
| Low-power device
| 100&nbsp;mA || 5&nbsp;V || 0.50&nbsp;W
|-
| Low-power SuperSpeed (USB 3.0) device
| 150&nbsp;mA || 5&nbsp;V || 0.75&nbsp;W
|-
| High-power device
| 500&nbsp;mA{{Efn|Up to 5 unit loads; with non-SuperSpeed devices, one unit load is 100&nbsp;mA.}} || 5&nbsp;V || 2.5&nbsp;W
|-
| High-power SuperSpeed (USB 3.0) device
| 900&nbsp;mA{{Efn|Up to 6 unit loads; with SuperSpeed devices, one unit load is 150&nbsp;mA.}} || 5&nbsp;V || 4.5&nbsp;W
|-
| Battery Charging (BC) 1.2
| 1.5&nbsp;A  || 5&nbsp;V || 7.5&nbsp;W
|-
| Single-lane SuperSpeed+ (USB 3.2 Gen2x1, and former USB 3.1 Gen2) device
| 1.5&nbsp;A{{Efn|name=Vml|Up to 6 unit loads; with multi-lane devices, one unit load is 250&nbsp;mA.}} || 5&nbsp;V || 7.5&nbsp;W
|-
|  Power Delivery 3.0 SPR
| 3&nbsp;A    || 5&nbsp;V || 15&nbsp;W
|-
|  Power Delivery 3.0 SPR
| 3&nbsp;A    || 9&nbsp;V || 27&nbsp;W
|-
|  Power Delivery 3.0 SPR
| 3&nbsp;A    || 15&nbsp;V || 45&nbsp;W
|-
|  Power Delivery 3.0 SPR
| 3&nbsp;A    || 20&nbsp;V || 60&nbsp;W
|-
| Power Delivery 3.0 SPR Type-C
| 5&nbsp;A{{efn|name="req_5A_cable"|>3&nbsp;A (>20&nbsp;W) operation requires an electronically marked cable rated at 5&nbsp;A.}} || 20&nbsp;V || 100&nbsp;W
|-
| Power Delivery 3.1 EPR Type-C
| 5&nbsp;A{{efn|name="req_5A_cable"}} || 28&nbsp;V{{efn|name="req_EPR_cable"|>20&nbsp;V (>60&nbsp;W) operation requires an electronically marked Extended Power Range (EPR) cable.}} || 140&nbsp;W
|-
| Power Delivery 3.1 EPR Type-C
| 5&nbsp;A{{efn|name="req_5A_cable"}} || 36&nbsp;V{{efn|name="req_EPR_cable"|>20&nbsp;V (>60&nbsp;W) operation requires an electronically marked Extended Power Range (EPR) cable.}} || 180&nbsp;W
|-
| Power Delivery 3.1 EPR Type-C
| 5&nbsp;A{{efn|name="req_5A_cable"}} || 48&nbsp;V{{efn|name="req_EPR_cable"|>20&nbsp;V (>60&nbsp;W) operation requires an electronically marked Extended Power Range (EPR) cable.}} || 240&nbsp;W
|-
| colspan=4 | {{Notelist}}
|}

The limit to device power draw is stated in terms of a ''unit load'' which is 100&nbsp;mA for USB 2.0, or 150&nbsp;mA for SuperSpeed (i.e. USB 3.''x'') devices. Low-power devices may draw at most 1 unit load, and all devices must act as low-power devices before they are configured. A high-powered device must be configured, after which it may draw up to 5 unit loads (500&nbsp;mA), or 6 unit loads (900&nbsp;mA) for SuperSpeed devices, as specified in its configuration because the maximum power may not always be available from the upstream port.<ref name="usb.org">{{cite web |url=http://www.usb.org/developers/docs/ |title=USB.org |website=USB.org |access-date=June 22, 2010 |url-status=live |archive-url=https://web.archive.org/web/20120619021820/http://www.usb.org/developers/docs |archive-date=June 19, 2012}}</ref><ref>{{cite web |url=http://esd.cs.ucr.edu/webres/usb11.pdf |title=Universal Serial Bus 1.1 Specification |date=September 23, 1998 |access-date=November 24, 2014 |website=cs.ucr.edu |pages=150, 158 |url-status=live |archive-url=https://web.archive.org/web/20150102233110/http://esd.cs.ucr.edu/webres/usb11.pdf |archive-date=January 2, 2015}}</ref><ref>{{cite web |url=http://www.usb.org/developers/docs/usb_20_070113.zip |title=Universal Serial Bus 2.0 Specification, Section 7.2.1.3 Low-power Bus-powered Functions |date=April 27, 2000 |access-date=January 11, 2014 |website=usb.org |format=ZIP |url-status=live |archive-url=https://web.archive.org/web/20130910140635/http://www.usb.org/developers/docs/usb_20_070113.zip |archive-date=September 10, 2013}}</ref><ref>{{cite web |url=http://www.usb.org/developers/docs/usb_20_070113.zip |title=Universal Serial Bus 2.0 Specification, Section 7.2.1.4 High-power Bus-powered Functions |date=April 27, 2000 |access-date=January 11, 2014 |website=usb.org |format=ZIP |url-status=live |archive-url=https://web.archive.org/web/20130910140635/http://www.usb.org/developers/docs/usb_20_070113.zip |archive-date=September 10, 2013}}</ref>

A bus-powered hub is a high-power device providing low-power ports. It draws 1 unit load for the hub controller and 1 unit load for each of at most 4 ports. The hub may also have some non-removable functions in place of ports. A self-powered hub is a device that provides high-power ports by supplementing the power supply from the host with its own external supply. Optionally, the hub controller may draw power for its operation as a low-power device, but all high-power ports must draw from the hub's self-power.

Where devices (for example, high-speed disk drives) require more power than a high-power device can draw,<ref>{{cite web |url=http://www.xbitlabs.com/articles/storage/display/25inch-500-640-750gb-hdd-roundup_17.html#sect0 |title=Roundup: 2.5-inch Hard Disk Drives with 500&nbsp;GB, 640&nbsp;GB and 750&nbsp;GB Storage Capacities (page 17) |website=xbitlabs.com |date=June 16, 2010 |access-date=July 9, 2010 |archive-url=https://web.archive.org/web/20100628183615/http://www.xbitlabs.com/articles/storage/display/25inch-500-640-750gb-hdd-roundup_17.html#sect0 |archive-date=June 28, 2010}}</ref> they function erratically, if at all, from bus power of a single port. USB provides for these devices as being self-powered. However, such devices may come with a Y-shaped cable that has two USB plugs (one for power and data, the other for only power), so as to draw power as two devices.<ref>{{cite web |url=http://www.hitachigst.com/hdd/support/SignatureMiniFAQ.html#a2 |title=I have the drive plugged in but I cannot find the drive in "My Computer", why? |website=hitachigst.com |access-date=March 30, 2012 |archive-url=https://web.archive.org/web/20110215144332/http://www.hitachigst.com/hdd/support/SignatureMiniFAQ.html#a2 |archive-date=February 15, 2011}}</ref> Such a cable is non-standard, with the USB compliance specification stating that "use of a 'Y' cable (a cable with two A-plugs) is prohibited on any USB peripheral", meaning that "if a USB peripheral requires more power than allowed by the USB specification to which it is designed, then it must be self-powered."<ref>{{cite web |url=http://compliance.usb.org/index.asp?UpdateFile=Policies#72 |title=USB-IF Compliance Updates |website=Compliance.usb.org |date=September 1, 2011 |access-date=January 22, 2014 |url-status=live |archive-url=https://web.archive.org/web/20140203192507/http://compliance.usb.org/index.asp?UpdateFile=Policies#72 |archive-date=February 3, 2014}}</ref>

{{Reflist|group="Power"}}

=== USB battery charging <span class="anchor" id="ACA"></span><span class="anchor" id="BCS"></span><span class="anchor" id="62680-3"></span>===
<!-- "USB Battery Charging" and "USB Battery Charging Specification 1.0" redirect here. -->
'''USB Battery Charging''' ('''BC''') defines a ''charging port'', which may be a ''charging downstream port'' (CDP), with data, or a ''dedicated charging port'' (DCP) without data. Dedicated charging ports can be found on USB power adapters to run attached devices and battery packs. Charging ports on a host with both kinds will be labeled.<ref name="USBBC1.2">{{cite web | url = https://usb.org/sites/default/files/BCv1.2_070312_0.zip | title = Battery Charging Specification, Revision 1.2 | date = March 15, 2012 | access-date = August 13, 2021 | publisher = USB Implementers Forum | url-status = live | archive-url = https://web.archive.org/web/20210310200454/https://usb.org/sites/default/files/BCv1.2_070312_0.zip | archive-date = March 10, 2021 }}</ref>

The charging device identifies a charging port by non-data signaling on the D+ and D− terminals. A dedicated charging port places a resistance not exceeding 200&nbsp;Ω across the D+ and D− terminals.{{r|USBBC1.2|p=§1.4.7; table 5-3}}<!-- Section 1.4.7: "Dedicated Charging Port", page 3. Table 5-3: "Resistances", page 46. Details omitted for brevity. -->

Per the base specification, any device attached to a ''standard downstream port'' (SDP) must initially be a low-power device, with high-power mode contingent on later USB configuration by the host. Charging ports, however, can immediately supply between 0.5 and 1.5&nbsp;A of current. The charging port must not apply current limiting below 0.5&nbsp;A, and must not shut down below 1.5&nbsp;A or before the voltage drops to 2&nbsp;V.<ref name="USBBC1.2"/>

Since these currents are larger than in the original standard, the extra voltage drop in the cable reduces noise margins, causing problems with High Speed signaling. Battery Charging Specification 1.1 specifies that charging devices must dynamically limit bus power current draw during High Speed signaling;<ref name="USBBC1.1">{{cite web | url = http://www.usb.org/developers/devclass_docs/batt_charging_1_1.zip | archive-url = https://web.archive.org/web/20140329080504/http://www.usb.org/developers/devclass_docs/batt_charging_1_1.zip | title = Battery Charging Specification, Revision 1.1 | date = April 15, 2009 | access-date=September 23, 2009 | archive-date = March 29, 2014 | publisher = USB Implementers Forum }}</ref> 1.2 specifies that charging devices and ports must be designed to tolerate the higher ground voltage difference in High Speed signaling.

Revision 1.2 of the specification was released in 2010. It made several changes, and increased limits including allowing 1.5&nbsp;A on charging downstream ports for unconfigured devices—allowing High Speed communication while having a current up to 1.5&nbsp;A. Also, support was removed for charging port detection via resistive mechanisms.<ref name="battchargespec1.2">{{cite web |url=http://www.usb.org/developers/docs/devclass_docs/BCv1.2_070312.zip |title=Battery Charging v1.2 Spec and Adopters Agreement |date=March 15, 2012 |access-date=May 13, 2021 |publisher=USB Implementers Forum |format=Zip |url-status=live |archive-url=https://web.archive.org/web/20141006113700/http://www.usb.org/developers/docs/devclass_docs/BCv1.2_070312.zip |archive-date=October 6, 2014 }}</ref>

{{anchor|Brick ID}}Before the Battery Charging Specification was defined, there was no standardized way for the portable device to inquire how much current was available. For example, Apple's [[iPod]] and [[iPhone]] chargers indicate the available current by voltages on the D− and D+ lines (sometimes also called "Apple Brick ID"). When D+ = D− = 2.0&nbsp;V, the device may pull up to 900&nbsp;mA. When D+ = 2.0&nbsp;V and D− = 2.8&nbsp;V, the device may pull up to 1&nbsp;A of current.<ref name=icharge>{{cite web | url = http://www.ladyada.net/make/mintyboost/icharge.html | title = Minty Boost — The mysteries of Apple device charging | website = Lady Ada | date = May 17, 2011 | archive-url = https://web.archive.org/web/20120328161525/http://www.ladyada.net/make/mintyboost/icharge.html | archive-date = March 28, 2012 }}</ref> When D+ = 2.8&nbsp;V and D− = 2.0&nbsp;V, the device may pull up to 2&nbsp;A of current.<ref>{{cite web |date= October 5, 2011 |url= http://www.instructables.com/id/Modify-a-cheap-USB-charger-to-feed-an-iPod-iPhone/ |title= Modify a cheap USB charger to feed an iPod, iPhone |url-status= live |archive-url= https://web.archive.org/web/20111007195308/http://www.instructables.com/id/Modify-a-cheap-USB-charger-to-feed-an-iPod-iPhone/ |archive-date= October 7, 2011 }}</ref>

==== Accessory charging adapters (ACA) ====
Portable devices having a [[USB On-The-Go]] port may want to charge and access a USB peripheral simultaneously, yet having only a single port (both due to On-The-Go and space requirement) prevents this. ''Accessory charging adapters (ACA)'' are devices that provide portable charging power to an On-The-Go connection between host and peripheral.

ACAs have three ports: the OTG port for the portable device, which is required to have a Micro-A plug on a captive cable; the accessory port, which is required to have a Micro-AB or type-A receptacle; and the charging port, which is required to have a Micro-B receptacle, or type-A plug or charger on a captive cable. The ID pin of the OTG port is not connected within plug as usual, but to the ACA itself, where signals outside the OTG floating and ground states are used for ACA detection and state signaling. The charging port does not pass data, but does use the D± signals for charging port detection. The accessory port acts as any other port. When appropriately signaled by the ACA, the portable device can charge from the bus power as if there were a charging port present; any OTG signals over bus power are instead passed to the portable device via the ID signal. Bus power is also provided to the accessory port from the charging port transparently.<ref name="USBBC1.2" />

===USB Power Delivery <span class="anchor" id="PD"></span><span class="anchor" id="PD-R1.0"></span><span class="anchor" id="PD-R2.0V1.0"></span>===
<!-- "USB Power Delivery" and "USB Power Delivery Specification" redirect here. -->
[[File:USB Type-C Charging Logo.svg|thumb|upright=0.5|The USB Type-C Charging logo ([[USB4]] 20&nbsp;Gbps port)]]

{| class="wikitable floatright" style=text-align:right
|+ USB PD Rev. 1.0 source profiles<ref name=PD1.0/>
|-
! Profile
!  +5&nbsp;V
! +12&nbsp;V
! +20&nbsp;V
|-
! 0
| colspan=3 {{n/a|Reserved}}
|-
! 1
| rowspan=5 valign="top" | 2.0&nbsp;A, 10&nbsp;W{{Efn|name="default-profile"|Default start-up profile}}
|           {{n/a}}
| rowspan=3 {{n/a}}
|-
! 2
| 1.5&nbsp;A, 18&nbsp;W
|-
! 3
| rowspan=2 valign="top" | 3.0&nbsp;A, 36&nbsp;W
|-
! 4
| 3.0&nbsp;A, 60&nbsp;W
|-
! 5
| 5.0&nbsp;A, 60&nbsp;W
| 5.0&nbsp;A, 100&nbsp;W
|-
| colspan=4 | {{Notelist}}
|}

{| class="wikitable floatright" style=text-align:right
|+ USB Power Delivery rev. 2.0/3.''x'' power rules
|-
! Power
! style=max-width:14em | Minimum USB‑C<br />cable required
! Voltage
! Current
|-
! ≤ 15&nbsp;W
! rowspan=4 | Any{{Efn-ua|name="60W"|''60&nbsp;W'' label required on both plug bodies by <br/>current standard, not required on older cables}}<ref name="USBPD20"/><ref name=USBPD30/><ref name=USBPD31/>
| 5&nbsp;V
| rowspan=4 | ≤ 3.0&nbsp;A
|-
! ≤ 27&nbsp;W
| 9&nbsp;V
|-
! ≤ 45&nbsp;W
| 15&nbsp;V
|-
! ≤ 60&nbsp;W
| 20&nbsp;V
|- style="border-top: double; border-bottom: double;"
! ≤ 100&nbsp;W
! 5&nbsp;A, or 100&nbsp;W{{Efn-ua|name="emarked-cable"|Electronically marked}}
| 20&nbsp;V
| halign="right" | ≤ 5.0&nbsp;A
|-
! ≤ 140&nbsp;W{{Efn-ua|name="EPR"|USB PD Extended Power Range}}
! rowspan=3 | 240&nbsp;W{{Efn-ua|name="emarked-cable"}}{{Efn-ua|name="240W"|''240&nbsp;W'' label required on both plug bodies}}<ref name=USBPD31/>
| 28&nbsp;V
| rowspan=3 | ≤ 5.0&nbsp;A
|-
! ≤ 180&nbsp;W{{Efn-ua|name="EPR"}}
| 36&nbsp;V
|-
! ≤ 240&nbsp;W{{Efn-ua|name="EPR"}}
| 48&nbsp;V
|-
| colspan=9 | {{Notelist-ua}}
|}

[[File:USB Power Delivery Extended Power Range up to 240Watt.svg|thumb|Power rule of USB Power Delivery Revision 3.1]]

In July 2012, the USB Promoters Group announced the finalization of the '''USB Power Delivery''' ('''USB-PD''') specification (USB PD rev. 1), an extension that specifies using certified ''PD aware'' USB cables with standard USB Type-A and Type-B connectors to deliver increased power (more than 7.5&nbsp;W maximum allowed by the previous [[#USB battery charging|USB Battery Charging]] specification) to devices with greater power demands. (USB-PD A and B plugs have a mechanical mark while Micro plugs have a resistor or capacitor attached to the ID pin indicating the cable capability.) USB-PD Devices can request higher currents and supply voltages from compliant hosts—up to 2&nbsp;A at 5&nbsp;V (for a power consumption of up to 10&nbsp;W), and optionally up to 3&nbsp;A or 5&nbsp;A at either 12&nbsp;V (36&nbsp;W or 60&nbsp;W) or 20&nbsp;V (60&nbsp;W or 100&nbsp;W).<ref>{{cite web|url=http://www.techspot.com/news/52321-usb-30-superspeed-update-to-eliminate-need-for-chargers.html|title=USB 3.0 SuperSpeed Update to Eliminate Need for Chargers |last=Burgess|first=Rick|date=April 22, 2013 |publisher=TechSpot}}</ref> In all cases, both host-to-device and device-to-host configurations are supported.<ref>{{cite web |url=http://www.usb.org/press/USB_Power_Delivery_Spec_Completion_FINAL_072712.pdf |title=USB 3.0 Promoter Group Announces Availability of USB Power Delivery Specification |date=July 18, 2012 |access-date=January 16, 2013 |url-status=live |archive-url=https://web.archive.org/web/20130120031237/http://www.usb.org/press/USB_Power_Delivery_Spec_Completion_FINAL_072712.pdf |archive-date=January 20, 2013 }}</ref>

The intent is to permit uniformly charging laptops, tablets, USB-powered disks and similarly higher-power consumer electronics, as a natural extension of existing European and Chinese mobile telephone charging standards. This may also affect the way electric power used for small devices is transmitted and used in both residential and public buildings.<ref name="usb-power-delivery">{{cite news |url= https://www.economist.com/news/international/21588104-humble-usb-cable-part-electrical-revolution-it-will-make-power-supplies?fsrc=scn/fb/wl/pe/edisonsrevenge |title= Edison's revenge |newspaper= The Economist |date= October 19, 2013 |access-date= October 23, 2013 |url-status= live |archive-url= https://web.archive.org/web/20131022091918/http://www.economist.com/news/international/21588104-humble-usb-cable-part-electrical-revolution-it-will-make-power-supplies?fsrc=scn%2Ffb%2Fwl%2Fpe%2Fedisonsrevenge |archive-date= October 22, 2013 }}</ref><ref name=PD1.0>{{cite web |url=http://www.usb.org/developers/powerdelivery/PD_1.0_Introduction.pdf |title=USB Power Delivery — Introduction |date=July 16, 2012 |access-date=January 6, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130123140132/http://www.usb.org/developers/powerdelivery/PD_1.0_Introduction.pdf |archive-date=January 23, 2013 }}</ref> The standard is designed to coexist with the previous [[#USB battery charging|USB Battery Charging]] specification.<ref>{{cite web|url=https://www.usb.org/usb-charger-pd|title=USB Power Delivery}}</ref>

The first Power Delivery specification (Rev. 1.0) defined six fixed power profiles for the power sources. PD-aware devices implement a flexible power management scheme by interfacing with the power source through a bidirectional data channel and requesting a certain level of electrical power, variable up to 5&nbsp;A and 20&nbsp;V depending on supported profile. The power configuration protocol can use [[Differential Manchester encoding|BMC]] coding over the CC (configuration channel) wire if one is present, or a 24&nbsp;MHz [[frequency-shift keying|BFSK]]-coded transmission channel on the V<sub>BUS</sub> line.<ref name="PD1.0" />

The USB Power Delivery specification revision&nbsp;2.0 (USB PD Rev. 2.0) has been released as part of the USB&nbsp;3.1 suite.<ref name="USBPD20">{{citation | title=Universal Serial Bus Power Delivery Specification revision&nbsp;2.0, version&nbsp;1.2 | chapter=10 Power Rules | date=March 25, 2016 | chapter-url=http://www.usb.org/developers/docs/ | publisher=USB Implementers Forum | access-date=April 9, 2016 | url-status=live | archive-url=https://archive.today/20240526002457/https://www.webcitation.org/685PPTw8f?url=http://www.usb.org/developers/docs/ | archive-date=May 26, 2024 }}</ref><ref>{{cite web|url=https://www.usb.org/documents|title=USB&nbsp;3.1 Specification |archive-url=https://web.archive.org/web/20120619021820/http://www.usb.org/developers/docs|archive-date=June 19, 2012|url-status=live|access-date=November 11, 2014}}</ref><ref>{{cite web |url=https://www.anandtech.com/show/8539/usb-power-delivery-v20-and-billboard-device-class-v10-specifications-finalized |title=USB Power Delivery v2.0 Specification Finalized - USB Gains Alternate Modes |website=AnandTech.com }}</ref> It covers the USB-C cable and connector with a separate configuration channel, which now hosts a [[DC coupled]] low-frequency [[biphase mark code|BMC]]-coded data channel that reduces the possibilities for [[USB 3.0 RF interference|RF interference]].<ref>{{cite web|title=USB Future Specifications Industry Reviews|url=http://www.usb.org/developers/USB-Futures.pdf|access-date=August 10, 2014|url-status=live|archive-url=https://web.archive.org/web/20140729083949/http://www.usb.org/developers/USB-Futures.pdf|archive-date=July 29, 2014}}</ref> Power Delivery protocols have been updated to facilitate USB-C features such as cable ID function, Alternate Mode negotiation, increased V<sub>BUS</sub> currents, and V<sub>CONN</sub>-powered accessories.

As of USB Power Delivery specification revision&nbsp;2.0, version&nbsp;1.2, the six fixed power profiles for power sources have been deprecated.<ref>{{citation | title=Universal Serial Bus Power Delivery Specification revision 2.0, version 1.2 | chapter=A. Power Profiles | date=March 25, 2016 | chapter-url=http://www.usb.org/developers/docs/usb_31_040816.zip | publisher=USB Implementers Forum | access-date=April 9, 2016 | archive-url=https://web.archive.org/web/20160412211620/http://www.usb.org/developers/docs/usb_31_040816.zip | archive-date=April 12, 2016 }}</ref> USB PD Power Rules replace power profiles, defining four normative voltage levels at 5&nbsp;V, 9&nbsp;V, 15&nbsp;V, and 20&nbsp;V. Instead of six fixed profiles, power supplies may support any maximum source output power from 0.5&nbsp;W to 100&nbsp;W.

{{Anchor|Programmable Power Supply|PPS}}
The USB Power Delivery specification revision&nbsp;3.0 defines an optional Programmable Power Supply (PPS) protocol that allows granular control over V<sub>BUS</sub> output, allowing a voltage range of 3.3 to 21 V in 20&nbsp;mV steps, and a current specified in 50&nbsp;mA steps, to facilitate constant-voltage and constant-current charging. Revision 3.0 also adds extended configuration messages and fast role swap and deprecates the BFSK protocol.<ref name="USBPD30">{{citation|title=Universal Serial Bus Power Delivery Specification revision&nbsp;3.0, version&nbsp;1.1|chapter-url=https://www.usb.org/documents|archive-url=https://archive.today/20240526002457/https://www.webcitation.org/685PPTw8f?url=http://www.usb.org/developers/docs/|url-status=live|chapter=10 Power Rules|publisher=USB Implementers Forum|access-date=September 5, 2017|archive-date=May 26, 2024}}</ref>{{rp|at=Table&nbsp;6.26}}<ref name="PD_HK2016">{{Cite web|url=http://www.usb.org/developers/presentations/USB_DevDays_Hong_Kong_2016_-_USB_PD.pdf|title=USB Power Delivery|date=October 20, 2016|website=usb.org|publisher=USB-IF |archive-url=https://web.archive.org/web/20161220102831/http://www.usb.org/developers/presentations/USB_DevDays_Hong_Kong_2016_-_USB_PD.pdf|archive-date=December 20, 2016}}</ref><ref>{{cite web |url=https://e2e.ti.com/blogs_/b/powerhouse/archive/2016/07/14/usb-power-delivery-2-vs-3 |title=USB Power Delivery 2.0 vs 3.0 |first=Deric |last=Waters |date=July 14, 2016 |website=E2E.TI.com |access-date=July 30, 2017 |url-status=live |archive-url=https://web.archive.org/web/20170730234342/https://e2e.ti.com/blogs_/b/powerhouse/archive/2016/07/14/usb-power-delivery-2-vs-3 |archive-date=July 30, 2017 }}</ref>

[[File:Certified USB Fast Charger 45W Logo.svg|thumb|upright=0.5|The Certified USB Fast Charger logo indicating support for the Programmable Power Supply (PPS) protocol in USB Power Delivery (PD) chargers]]

On January 8, 2018, USB-IF announced the Certified USB Fast Charger logo for chargers that use the Programmable Power Supply (PPS) protocol from the USB Power Delivery 3.0 specification.<ref>{{cite press release|url=https://www.businesswire.com/news/home/20180108005383/en/USB-IF-Introduces-Fast-Charging-Expand-Certified-USB|title=USB-IF Introduces Fast Charging to Expand its Certified USB Charger Initiative|date=January 9, 2018|access-date=January 10, 2018}}</ref>

{{Anchor|Extended Power Range|EPR}}
In May 2021, the USB PD promoter group launched revision 3.1 of the specification.<ref name="USBPD31">{{citation|title=Universal Serial Bus Power Delivery Specification revision&nbsp;3.1, version&nbsp;1.0|chapter-url=https://usb.org/document-library/usb-power-delivery|chapter=10 Power Rules|publisher=USB Implementers Forum|access-date=September 5, 2017}}</ref> Revision 3.1 adds Extended Power Range (EPR) mode which allows higher voltages of 28, 36, and 48 V, providing up to 240 W of power (48 V at 5 A), and the "Adjustable Voltage Supply" (AVS) protocol which allows specifying the voltage from a range of 15 to 48 V in 100 mV steps.<ref>[https://www.eenewseurope.com/news/usb-pd-boosts-usb-c-power-delivery-240w-48v USB-PD boosts USB-C power delivery to 240W at 48V]. Nick Flaherty, EENews. May 28, 2021</ref><ref>[https://www.anandtech.com/show/16712/usbc-power-delivery-hits-240w-with-extended-power-range  USB-C Power Delivery Hits 240W with Extended Power Range]. Ganesh T S, Anandtech. May 28, 2021</ref> Higher voltages require electronically marked EPR cables that support 5 A operation and incorporate mechanical improvements required by the USB Type-C standard rev. 2.1; existing power modes are retroactively renamed Standard Power Range (SPR). In October 2021 Apple introduced a  140 W (28 V 5 A) [[Gallium nitride#Transistors and power ICs|GaN]] USB PD charger with new MacBooks,<ref>{{Cite web|date=October 30, 2021|title=Teardown of Brand New Apple 140W USB-C GaN Charger|url=https://www.chargerlab.com/teardown-of-brand-new-apple-140w-usb-c-gan-charger/|access-date=November 15, 2021}}</ref> and in June 2023 Framework introduced a 180 W (36 V 5 A) GaN USB PD charger with the Framework 16.<ref>{{Cite web |title=Framework Laptop 16 Deep Dive - 180W Power Adapter |url=https://frame.work/blog/framework-laptop-16-deep-dive---180w-power-adapter |access-date=February 28, 2024 |website=Framework }}</ref>

In October 2023, the USB PD promoter group launched revision 3.2 of the specification. The AVS protocol now works with the old standard power range (SPR), down to a minimum of 9&nbsp;V.<ref name="USBPD32">{{citation|title=Universal Serial Bus Power Delivery Specification revision&nbsp;3.2, version&nbsp;1.0|url=https://www.usb.org/sites/default/files/USB%20PD%20R3.2%20V1.0_1.zip|publisher=USB Implementers Forum|access-date=February 13, 2023}}</ref>{{rp|at=&sect;10.2.2}}

Prior to Power Delivery, mobile phone vendors used custom protocols to exceed the 7.5&nbsp;W cap on the [[USB Battery Charging]] Specification (BCS). For example, Qualcomm's [[Quick Charge]] 2.0 is able to deliver 18&nbsp;W at a higher voltage, and [[VOOC]] delivers 20&nbsp;W at the normal 5&nbsp;V.<ref>{{Cite web |url=https://www.cnet.com/news/fast-charging-phones-quick-charge-dash-charging/ |title=How fast can a fast-charging phone charge if a fast-charging phone can charge really fast? |website=CNet |access-date=December 4, 2016 }}</ref> Some of these technologies, such as Quick Charge 4, eventually became compatible with USB PD again.<ref>{{Cite web |url=http://www.anandtech.com/show/10846/qualcomm-announces-quick-charge-4 |title=Qualcomm Announces Quick Charge 4: Supports USB Type-C Power Delivery |work=AnandTech |access-date= December 13, 2016}}</ref>

=== Charge controllers ===
As of 2024 mainstream USB PD charging controllers support up to 100&nbsp;W through a single port, with a few up to 140&nbsp;W<ref>{{cite web |title=Teardown of Anker 140W PD3.1 USB-C GaN Charger (717 Charger) |date=October 26, 2022 |url=https://www.chargerlab.com/teardown-of-anker-140w-pd3-1-usb-c-gan-charger-717-charger/}}</ref><ref>{{citation |title=140W PD 3.1 Power Adapters, the future of USB C Power Delivery | date=January 2, 2023 |url=https://www.youtube.com/watch?v=x4euVfT1ksk |access-date=March 8, 2024}}</ref> and custom built up to 180&nbsp;W.<ref>{{cite web |title=Framework Laptop 16 Deep Dive - 180W Power Adapter |url=https://frame.work/au/en/blog/framework-laptop-16-deep-dive---180w-power-adapter |access-date=March 8, 2024 |website=Framework}}</ref>

=== Sleep-and-charge ports ===
[[File:Thinkpad X220 Yellow USB.jpg|thumb|A yellow USB port denoting sleep-and-charge]]

Sleep-and-charge USB ports can be used to charge electronic devices even when the computer that hosts the ports is switched off. Normally, when a computer is powered off the USB ports are powered down. This feature has also been implemented on some laptop docking stations allowing device charging even when no laptop is present.<ref>{{cite web|title=ThinkPad Ultra Dock|url=http://shop.lenovo.com/us/en/itemdetails/40A20090US/460/76C432D671BE45E6A425ED543A9591C2|website=lenovo.com|access-date=September 16, 2016|url-status=live|archive-url=https://web.archive.org/web/20160917084037/http://shop.lenovo.com/us/en/itemdetails/40A20090US/460/76C432D671BE45E6A425ED543A9591C2|archive-date=September 17, 2016}}</ref> On laptops, charging devices from the USB port when it is not being powered from AC drains the laptop battery; most laptops have a facility to stop charging if their own battery charge level gets too low.<ref>{{cite web |url= http://www.mytoshiba.com.au/file/download/resource/file/12585/NB200-UserGuide.pdf |title= Toshiba NB200 User Manual |location= UK |date= March 1, 2009 |access-date= January 26, 2014 |url-status= live |archive-url= https://web.archive.org/web/20140219115326/http://www.mytoshiba.com.au/file/download/resource/file/12585/NB200-UserGuide.pdf |archive-date= February 19, 2014 }}</ref>

On Dell, HP and Toshiba laptops, sleep-and-charge USB ports are marked with the standard USB symbol with an added lightning bolt or battery icon on the right side.<ref>{{cite web | url = https://www.dell.com/support/article/nl-nl/sln155147/usb-powershare-feature-on-dell-laptops?lang=en | title = USB PowerShare Feature | date = September 15, 2019 | access-date = June 15, 2020 | website = dell.com }}</ref> Dell calls this feature ''PowerShare'',<ref>{{cite web | url = http://www.dell.com/support/troubleshooting/an/en/andhs1/KCS/KcsArticles/ArticleView?c=an&l=en&s=dhs&docid=608993 | title = USB PowerShare Feature | date = June 5, 2013 | access-date = December 4, 2013 | website = dell.com | url-status = live | archive-url = https://web.archive.org/web/20131108231014/http://www.dell.com/support/troubleshooting/an/en/andhs1/KCS/KcsArticles/ArticleView?c=an&l=en&s=dhs&docid=608993 | archive-date = November 8, 2013 }}</ref> and it needs to be enabled in the BIOS. Toshiba calls it ''USB Sleep-and-Charge''.<ref>{{cite web | url = http://www.toshiba.com/us/sleep-and-charge | title = USB Sleep-and-Charge Ports | access-date = December 21, 2014 | website = toshiba.com | url-status = live | archive-url = https://web.archive.org/web/20141214094949/http://www.toshiba.com/us/sleep-and-charge | archive-date = December 14, 2014 }}</ref> On [[Acer Inc.]] and [[Packard Bell]] laptops, sleep-and-charge USB ports are marked with a non-standard symbol (the letters ''USB'' over a drawing of a battery); the feature is called ''Power-off USB''.<ref>{{cite web | url = http://packard-bell-scandic.custhelp.com/app/answers/detail/a_id/29967/~/usb-charge-manager | title = USB Charge Manager | access-date = April 25, 2014 | website = packardbell.com}}</ref> [[Lenovo]] calls this feature ''Always On USB''.<ref>{{Cite web|url=https://support.lenovo.com/nl/en/solutions/ht503671|title=How to configure the system to charge devices over USB port when it is off - idea/Lenovo laptops - NL|website=support.lenovo.com|access-date=April 7, 2020}}</ref>

=== Mobile device charger standards ===
{{Main|Universal charger}}
==== In China ====
{{As of |2007|6|14}}, all new [[mobile phone]]s applying for a license in [[China]] are required to use a USB port as a power port for battery charging.<ref>{{cite magazine | url = http://www.eetimes.com/rss/showArticle.jhtml?articleID=199800238&cid=RSSfeed_eetimes_newsRSS | title = China to enforce universal cell phone charger | magazine = EE Times | author = Cai Yan | date = May 31, 2007 | access-date = August 25, 2007 | url-status = live | archive-url = https://web.archive.org/web/20070929095523/http://www.eetimes.com/rss/showArticle.jhtml?articleID=199800238&cid=RSSfeed_eetimes_newsRSS | archive-date = September 29, 2007 }}</ref><ref>The Chinese technical standard: {{Cite web | url = http://www.dianyuan.com/bbs/u/63/2015571206841181.pdf | title = YD/T 1591-2006, Technical Requirements and Test Method of Charger and Interface for Mobile Telecommunication Terminal Equipment | language = zh |website=Dian yuan | archive-url = https://web.archive.org/web/20110515212645/http://www.dianyuan.com/bbs/u/63/2015571206841181.pdf | archive-date = May 15, 2011 }}</ref> This was the first standard to use the convention of shorting D+ and D− in the charger.<ref>{{cite web |first1=Crystal |last1=Lam |first2=Harry |last2=Liu |url=http://www.eetimes.com/document.asp?doc_id=1275077&print=yes |title=How to conform to China's new mobile phone interface standards |publisher=Wireless Net DesignLine |date=October 22, 2007 |access-date=June 22, 2010 |url-status=live |archive-url=https://web.archive.org/web/20140514165523/http://www.eetimes.com/document.asp?doc_id=1275077&print=yes |archive-date=May 14, 2014 }}</ref>

==== OMTP/GSMA Universal Charging Solution ====
In September 2007, the [[Open Mobile Terminal Platform]] group (a forum of mobile network operators and manufacturers such as [[Nokia]], [[Samsung]], [[Motorola]], [[Sony Ericsson]], and [[LG]]) announced that its members had agreed on Micro-USB as the future common connector for mobile devices.<ref>{{cite news |url=http://www.news.com/2100-1041_3-6209247.html |title=Pros Seem to Outdo Cons in New Phone Charger Standard |website=News.com |date=September 20, 2007 |access-date=November 26, 2007 }}</ref><ref>{{cite press release |url=http://www.omtp.org/News/Display.aspx?Id=4ec69ecb-0978-4df6-b045-34557aabbcbd |title=Broad Manufacturer Agreement Gives Universal Phone Cable Green Light |publisher=OTMP |date=September 17, 2007 |access-date=November 26, 2007 |archive-url=https://web.archive.org/web/20090629183154/http://www.omtp.org/News/Display.aspx?Id=4ec69ecb-0978-4df6-b045-34557aabbcbd |archive-date=June 29, 2009 }}</ref>

The [[GSM Association]] (GSMA) followed suit on February 17, 2009,<ref name="gsm20090217">{{Cite press release | url= http://www.gsmworld.com/newsroom/press-releases/2009/2548.htm | publisher= GSM World | title= Agreement on Mobile phone Standard Charger | archive-url= https://web.archive.org/web/20090217192039/http://www.gsmworld.com//newsroom//press-releases//2009//2548.htm | archive-date= February 17, 2009 }}</ref><ref>{{cite web|url=http://www.omtp.org/Publications/Display.aspx?Id=4dda105f-8472-4c12-ba04-75dd3c1d4ca6 |title=Common Charging and Local Data Connectivity |publisher=[[Open Mobile Terminal Platform]] |date=February 11, 2009 |access-date=February 11, 2009 |archive-url=https://web.archive.org/web/20090329233721/http://www.omtp.org/Publications/Display.aspx?Id=4dda105f-8472-4c12-ba04-75dd3c1d4ca6 |archive-date=March 29, 2009 }}</ref><ref>{{cite web |url=http://www.gsmworld.com/our-work/mobile_planet/universal_charging_solution.htm |title=Universal Charging Solution ~ GSM World |publisher=GSM world |access-date=June 22, 2010 |archive-url=https://web.archive.org/web/20100626073016/http://www.gsmworld.com/our-work/mobile_planet/universal_charging_solution.htm |archive-date=June 26, 2010 }}</ref><ref>{{cite web |url= http://www.planetanalog.com/article/printableArticle.jhtml?articleID=218501515 |archive-url= https://archive.today/20120909022205/http://www.planetanalog.com/article/printableArticle.jhtml?articleID=218501515 |archive-date= September 9, 2012 |title= Meeting the challenge of the universal charge standard in mobile phones |publisher=Planet Analog |access-date=June 22, 2010 }}</ref> and on April 22, 2009, this was further endorsed by the [[CTIA (organization)|CTIA – The Wireless Association]],<ref>{{cite press release | url = http://www.ctia.org/media/press/body.cfm/prid/1817 | title = The Wireless Association Announces One Universal Charger Solution to Celebrate Earth Day | publisher = CTIA | date = April 22, 2009 | access-date = June 22, 2010 | archive-url = https://web.archive.org/web/20101214154849/http://ctia.org/media/press/body.cfm/PRID/1817 | archive-date = December 14, 2010 }}</ref> with the [[International Telecommunication Union]] (ITU) announcing on October 22, 2009, that it had also embraced the Universal Charging Solution as its "energy-efficient one-charger-fits-all new mobile phone solution," and added: "Based on the Micro-USB interface, UCS chargers will also include a 4-star or higher efficiency rating—up to three times more energy-efficient than an unrated charger."<ref>{{cite press release |url=http://www.itu.int/newsroom/press_releases/2009/49.html |title=Universal Phone Charger Standard Approved |publisher=ITU |date=October 22, 2009 |access-date=May 22, 2023 |archive-url=https://web.archive.org/web/20100327101058/http://www.itu.int/newsroom/press_releases/2009/49.html |archive-date=March 27, 2010 }}</ref>

==== EU smartphone power supply standard ====
In June 2009, the [[European Commission]] organized a voluntary Memorandum of Understanding (MoU) to adopt micro-USB as a common standard for charging smartphones marketed in the [[European Union]]. The specification was called the [[common external power supply]]. The MoU lasted until 2014. The common EPS specification (EN 62684:2010) references the USB Battery Charging Specification and is similar to the GSMA/OMTP and Chinese charging solutions.<ref>{{cite web | url = http://ec.europa.eu/enterprise/rtte/chargers.htm | title = chargers | location = EU | publisher = EC | date = June 29, 2009 | access-date = June 22, 2010 | archive-url = https://web.archive.org/web/20091023232430/http://ec.europa.eu/enterprise/rtte/chargers.htm | archive-date = October 23, 2009 }}</ref><ref>{{cite magazine |url=https://www.wired.com/gadgetlab/2009/06/europe-gets-universal-cellphone-charger-in-2010/ |title=Europe gets universal cellphone charger in 2010 |magazine=Wired |date=June 13, 2009 |access-date=June 22, 2010 |url-status=live |archive-url=https://web.archive.org/web/20100818031835/http://www.wired.com/gadgetlab/2009/06/europe-gets-universal-cellphone-charger-in-2010/ |archive-date=August 18, 2010 }}</ref> In January 2011, the [[International Electrotechnical Commission|International Electrotechnical Commission (IEC)]] released its version of the (EU's) common EPS standard as IEC 62684:2011.<ref>{{cite web |url=http://www.iec.ch/newslog/2011/nr0311.htm |title=One size-fits-all mobile phone charger: IEC publishes first globally relevant standard |publisher=International Electrotechnical Commission |date=February 1, 2011 |access-date=February 20, 2012 |url-status=live |archive-url=https://web.archive.org/web/20120103141101/http://www.iec.ch/newslog/2011/nr0311.htm |archive-date=January 3, 2012 }}</ref>

In 2022, the [[Radio Equipment Directive (2022)|Radio Equipment Directive 2022/2380]] made USB-C compulsory as a mobile phone charging standard from 2024, and for laptops from 2026.<ref>{{Cite web |date=April 20, 2022 |title=Common charger: MEPs agree on proposal to reduce electronic waste |url=https://www.europarl.europa.eu/news/en/press-room/20220412IPR27115/common-charger-meps-agree-on-proposal-to-reduce-electronic-waste |archive-url=https://web.archive.org/web/20220422162233/https://www.europarl.europa.eu/news/en/press-room/20220412IPR27115/common-charger-meps-agree-on-proposal-to-reduce-electronic-waste |archive-date=April 22, 2022 |access-date=April 20, 2022 |website=European Parliament}}</ref>

=== Faster-charging standards ===
A variety of (non-USB) standards support charging devices faster than the [[#USB battery charging|USB Battery Charging]] standard. When a device doesn't recognize the faster-charging standard, generally the device and the charger fall back to the USB battery-charging standard of 5&nbsp;V at 1.5&nbsp;A (7.5&nbsp;W). When a device detects it is plugged into a charger with a compatible faster-charging standard, the device pulls more current or the device tells the charger to increase the voltage or both to increase power (the details vary between standards).<ref name="kumar">{{cite magazine |first1=Ajay |last1=Kumar |first2=Steven |last2=Winkelman |first3=Dave |last3=LeClair |url=https://www.pcmag.com/article/359908/what-is-fast-charging |title=What Is Fast Charging? |date=July 27, 2022<!--"Updated"; originally 2018 we believe--> |magazine=PCMag |access-date=May 21, 2023 }}</ref>

Such standards include:<ref name="kumar" /><ref name=digitaltrends-20210701>{{cite web |url=https://www.digitaltrends.com/mobile/how-does-fast-charging-work/ |title=How does fast charging work? Here's every single standard compared |last1=Hill |first1=Simon |last2=Revilla |first2=Andre |last3=Chandler |first3=Simon |website=Digital Trends |date=July 1, 2021 |access-date=August 20, 2022}}</ref>

* [[Anker Innovations|Anker]] PowerIQ
* [[Google]] fast charging
* [[Huawei]] SuperCharge
* [[MediaTek]] [[Pump Express]]
* [[Motorola Mobility|Motorola]] TurboPower
* Oppo Super [[VOOC]] Flash Charge, are also known as ''Dash Charge'' or ''Warp Charge'' on [[OnePlus]] devices and ''Dart Charge'' on [[Realme]] devices
* Qualcomm [[Quick Charge]] (QC)
* Samsung Adaptive Fast Charging

=== Non-standard devices ===
Some USB devices require more power than is permitted by the specifications for a single port. This is common for external hard and [[optical disc drive]]s, and generally for devices with [[electrical motor|motors]] or [[electrical lamp|lamps]]. Such devices can use an [[wall wart|external power supply]], which is allowed by the standard, or use a dual-input USB cable, one input of which is for power and data transfer, the other solely for power, which makes the device a non-standard USB device. Some USB ports and external hubs can, in practice, supply more power to USB devices than required by the specification but a standard-compliant device may not depend on this.

In addition to limiting the total average power used by the device, the USB specification limits the [[inrush current]] (i.e., the current used to charge decoupling and [[filter capacitor]]s) when the device is first connected. Otherwise, connecting a device could cause problems with the host's internal power. USB devices are also required to automatically enter ultra low-power suspend mode when the USB host is suspended. Nevertheless, many USB host interfaces do not cut off the power supply to USB devices when they are suspended.<ref>{{cite web|title=Part 2 - Electrical|url=http://www.usbmadesimple.co.uk/ums_2.htm|publisher=MQP Electronics |access-date=December 29, 2014|url-status=live|archive-url=https://web.archive.org/web/20141224203350/http://www.usbmadesimple.co.uk/ums_2.htm|archive-date=December 24, 2014}}</ref>

Some non-standard USB devices use the 5&nbsp;V power supply without participating in a proper USB network, which negotiates power draw with the host interface. Examples include USB-powered keyboard lights, fans, mug coolers and heaters, battery chargers, miniature [[vacuum cleaner]]s, and even miniature [[lava lamp]]s. In most cases, these items contain no digital circuitry, and thus are not standard-compliant USB devices. This may cause problems with some computers, such as drawing too much current and damaging circuitry. Prior to the USB Battery Charging Specification, the USB specification required that devices connect in a low-power mode (100&nbsp;mA maximum) and communicate their current requirements to the host, which then permits the device to switch into high-power mode.

Some devices, when plugged into charging ports, draw even more power (10&nbsp;watts) than the Battery Charging Specification allows—the [[iPad]] is one such device;<ref>{{cite web |url=http://www.macobserver.com/tmo/article/watt_to_know_about_iphone_ipad_power_adapters/ |title=Watt to Know About iPhone & iPad Power Adapters &#124; Analysis |publisher=The Mac Observer |access-date=December 12, 2011 |url-status=live |archive-url=https://web.archive.org/web/20111210104210/http://www.macobserver.com/tmo/article/watt_to_know_about_iphone_ipad_power_adapters/ |archive-date=December 10, 2011 }}</ref> it negotiates the current pull with data pin voltages.<ref name=icharge/> [[Barnes & Noble]] [[Nook Color]] devices also require a special charger that runs at 1.9&nbsp;A.<ref>{{cite web |url=http://bookclubs.barnesandnoble.com/t5/NOOK-Color-General-Discussion/Nook-Color-charger-uses-special-micro-USB-connector/td-p/1093812 |title=Nook Color charger uses special Micro-USB connector |website=barnesandnoble.com |date=July 3, 2011 |archive-url=https://web.archive.org/web/20120211135735/http://bookclubs.barnesandnoble.com/t5/NOOK-Color-General-Discussion/Nook-Color-charger-uses-special-micro-USB-connector/td-p/1093812 |archive-date=February 11, 2012 }}</ref>

=== PoweredUSB ===
{{Main|PoweredUSB}}

PoweredUSB is a proprietary extension that adds four pins supplying up to 6&nbsp;A at 5&nbsp;V, 12&nbsp;V, or 24&nbsp;V. It is commonly used in [[point of sale]] systems to power peripherals such as [[barcode reader]]s, [[credit card terminal]]s, and printers.

==See also==
* [[USB adapter]]
* [[USB communications]]

==References==
{{Reflist}}

{{USB}}

[[Category:USB]]