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 conrolled 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

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Basic support
Chrome Full support 61Edge No support NoFirefox No support NoIE No support NoOpera Full support 48Safari No support NoWebView Android No support NoChrome Android Full support 61Edge Mobile No support NoFirefox Android No support NoOpera Android Full support 48Safari iOS No support NoSamsung Internet Android No support No


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

Document Tags and Contributors

Contributors to this page: jpmedley
Last updated by: jpmedley,