USBDevice: opened property

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

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

Note: This feature is available in Web Workers.

The opened read only property of the USBDevice interface indicates whether a session has been started with a paired USB device. A device must be opened before it can be controlled by a web page.

Value

Examples

This example is for a hypothetical USB device with a multi-colored LED. It shows how to test that a device is open before calling USBDevice.controlTransferOut to set a specified LED color.

Note: What data can be passed to a USB device and how it is passed is particular and unique to each device.

js
async function setDeviceColor(usbDevice, r, g, b) {
  if (device.opened) {
    // This hypothetical USB device requires that the data passed to
    // it be in a Uint8Array.
    const payload = new Uint8Array([r, g, b]);

    await usbDevice.controlTransferOut(
      {
        requestType: "vendor",
        recipient: "device",
        request: 1,
        value: 0,
        index: 0,
      },
      payload,
    );
  }
}

Specifications

Specification
WebUSB API
# ref-for-dom-usbdevice-opened

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
opened
Experimental

Legend

Tip: you can click/tap on a cell for more information.

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