USBEndpoint

Secure context
This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.

The USBEndpoint interface of the WebUSB API provides information about an endpoint provided by the USB device. An endpoint represents a unidirectional data stream into or out of a device.

Constructor

USBEndpoint.USBEndpoint
Creates a new USBEndpoint object which will be populated with information about the endpoint on the provided USBAltenateInterface with the given endpoint number and transfer direction.

Properties

USBEndpoint.endpointNumber
Returns this endpoint's "endpoint number" which is a value from 1 to 15 extracted from the bEndpointAddress field of the endpoint descriptor defining this endpoint. This value is used to identify the endpoint when calling methods on USBDevice.
USBEndpoint.direction
Returns the direction in which this endpoint transfers data, one of:
  • "in" - Data is transferred from device to host.
  • "out" - Data is transferred from host to device.
USBEndpoint.type
Returns the type of this endpoint, one of:
  • "bulk" - Provides reliable data transfer for large payloads. Data sent through a bulk endpoint is guaranteed to be delivered or generate an error but may be preempted by other data traffic.
  • "interrupt" - Provides reliable data transfer for small payloads. Data sent through an interrupt endpoint is guaranteed to be delivered or generate an error and is also given dedicated bus time for transmission.
  • "isochronous" - Provides unreliable data transfer for payloads that must be delivered periodically. They are given dedicated bus time but if a deadline is missed the data is dropped.
USBEndpoint.packetSize
Returns the size of the packets that data sent through this endpoint will be divided into.

Examples

While sometimes the developer knows ahead of time the exact layout of a device's endpoints there are cases where this must be discovered at runtime. For example, a USB serial device must provide bulk input and output endpoints but their endpoint numbers will depend on what other interfaces the device provides.

This code identifies the correct endpoints by searching for the interface implementing the USB CDC interface class and then identifying the candidate endpoints based on their type and direction.

let inEndpoint = undefined;
let outEndpoint = undefined;

for (const interface of device.configuration.interfaces) {
  // Only support devices with out multiple alternate interfaces.
  const alternate = interface.alternates[0];

  // Identify the interface implementing the USB CDC class.
  const USB_CDC_CLASS = 10;
  if (alternate.interfaceClass != USB_CDC_CLASS) {
    continue;
  }

  for (const endpoint of alternate.endpoints) {
    // Identify the bulk transfer endpoints.
    if (endpoint.type != "bulk") {
      continue;
    }

    if (endpoint.direction == "in") {
      inEndpoint = endpoint.endpointNumber;
    } else if (endpoint.direction == "out") {
      outEndpoint = endpoint.endpointNumber;
    }
  }
}

Specifications

Specification Status Comment
WebUSB
The definition of 'USBEndPoint' in that specification.
Draft Initial definition.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
USBEndpoint
Experimental
Chrome Full support 61Edge Full support 79Firefox No support NoIE No support NoOpera Full support 48Safari No support NoWebView Android No support NoChrome Android Full support 61Firefox Android No support NoOpera Android Full support 45Safari iOS No support NoSamsung Internet Android Full support 8.0
USBEndpoint() constructor
Experimental
Chrome Full support 61Edge Full support 79Firefox No support NoIE No support NoOpera Full support 48Safari No support NoWebView Android No support NoChrome Android Full support 61Firefox Android No support NoOpera Android Full support 45Safari iOS No support NoSamsung Internet Android Full support 8.0
direction
Experimental
Chrome Full support 61Edge Full support 79Firefox No support NoIE No support NoOpera Full support 48Safari No support NoWebView Android No support NoChrome Android Full support 61Firefox Android No support NoOpera Android Full support 45Safari iOS No support NoSamsung Internet Android Full support 8.0
endpointNumber
Experimental
Chrome Full support 61Edge Full support 79Firefox No support NoIE No support NoOpera Full support 48Safari No support NoWebView Android No support NoChrome Android Full support 61Firefox Android No support NoOpera Android Full support 45Safari iOS No support NoSamsung Internet Android Full support 8.0
packetSize
Experimental
Chrome Full support 61Edge Full support 79Firefox No support NoIE No support NoOpera Full support 48Safari No support NoWebView Android No support NoChrome Android Full support 61Firefox Android No support NoOpera Android Full support 45Safari iOS No support NoSamsung Internet Android Full support 8.0
type
Experimental
Chrome Full support 61Edge Full support 79Firefox No support NoIE No support NoOpera Full support 48Safari No support NoWebView Android No support NoChrome Android Full support 61Firefox Android No support NoOpera Android Full support 45Safari iOS No support NoSamsung Internet Android Full support 8.0

Legend

Full support  
Full support
No support  
No support
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.