Web/API/USBEndpoint

Secure contextThis 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
WebUSBThe definition of 'USBEndPoint' in that specification.	Draft	Initial definition.

Browser compatibility

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
USBEndpoint Experimental'	Chrome Full support 61	Edge Full support 79	Firefox No support No	IE No support No	Opera Full support 48	Safari No support No	WebView Android No support No	Chrome Android Full support 61	Firefox Android No support No	Opera Android Full support 45	Safari iOS No support No	Samsung Internet Android Full support 8.0
USBEndpoint() constructor Experimental'	Chrome Full support 61	Edge Full support 79	Firefox No support No	IE No support No	Opera Full support 48	Safari No support No	WebView Android No support No	Chrome Android Full support 61	Firefox Android No support No	Opera Android Full support 45	Safari iOS No support No	Samsung Internet Android Full support 8.0
direction Experimental'	Chrome Full support 61	Edge Full support 79	Firefox No support No	IE No support No	Opera Full support 48	Safari No support No	WebView Android No support No	Chrome Android Full support 61	Firefox Android No support No	Opera Android Full support 45	Safari iOS No support No	Samsung Internet Android Full support 8.0
endpointNumber Experimental'	Chrome Full support 61	Edge Full support 79	Firefox No support No	IE No support No	Opera Full support 48	Safari No support No	WebView Android No support No	Chrome Android Full support 61	Firefox Android No support No	Opera Android Full support 45	Safari iOS No support No	Samsung Internet Android Full support 8.0
packetSize Experimental'	Chrome Full support 61	Edge Full support 79	Firefox No support No	IE No support No	Opera Full support 48	Safari No support No	WebView Android No support No	Chrome Android Full support 61	Firefox Android No support No	Opera Android Full support 45	Safari iOS No support No	Samsung Internet Android Full support 8.0
type Experimental'	Chrome Full support 61	Edge Full support 79	Firefox No support No	IE No support No	Opera Full support 48	Safari No support No	WebView Android No support No	Chrome Android Full support 61	Firefox Android No support No	Opera Android Full support 45	Safari iOS No support No	Samsung 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.

USBEndpoint by Mozilla Contributors is licensed under CC-BY-SA 2.5.