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

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.


var serialNumber = USBDevice.opened


A boolean.


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.

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

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

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


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

Browser compatibility

ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
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


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