a USB device does not appear in the WebUSB chooser
Nothing useful can be tested until the device or browser path is visible. Start with connection, power, permission and OS recognition before app settings.
Do not jump to the most invasive fix
Do not install unofficial driver packs or firmware from download sites just because the device is missing.
Retest the same condition
The first milestone is simple detection. Only after the device appears should you troubleshoot signal quality or app behavior.
Rule out the simple causes
- 1
Confirm WebUSB support and HTTPS.
- 2
Reconnect the USB device directly rather than through an unpowered hub.
- 3
Understand that many USB devices are owned by OS drivers and are intentionally unavailable to WebUSB.
Work through the problem in order
- 1
Try the device's standard browser API first if it is a keyboard, mouse, camera, audio device, or gamepad.
- 2
If the manufacturer documents WebUSB support, verify the required mode/interface.
- 3
A missing WebUSB entry is not a reliable indicator of a broken USB device.
If the matching DeviceOK test succeeds, prioritize the affected app, browser policy, operating-system setting, or configuration before assuming complete hardware failure.
If the same capability also fails in DeviceOK and another trusted diagnostic path, broaden the investigation to connection, operating-system/device state, official driver or firmware support, and finally hardware.