When connecting the micro:bit to a computer, it will automatically install a driver to your machine that enables it to communicate as a serial device via USB. There are some cases in which the driver being missing (Windows 7) or a legacy driver being present (Windows 8.1+) could cause an issue with the serial function or with WebUSB.

You should always start with our article on fault finding that covers common issues like USB cables not working.

Windows 7 (serial not working)

In Windows 7, you had to manually install the Mbed serial driver to enable the serial port. The legacy mBed driver is still available, but as Windows 7 reaches end of life you should upgrade your operating system accordingly.

Windows 8.1/10 (WebUSB not working)

If the Mbed Serial driver has been manually installed it might interfere with the Windows 8.1/10 automatic installation of the WebUSB driver. 

It is possible that a driver was previously installed on the Windows machine if you have upgraded from Windows 7

To check if you have this driver already:

  1.  Open Windows Device Manager and see if the micro:bit USB device is shown. If it is...

  2. find the mbed Composite Device entry, right click on it and select Uninstall device.

  3. A new window will open, mark the Delete the driver software for this device box and click Uninstall.

  4. Unplug and replug your micro:bit and it should appear under USB devices.