Uploading from Firefox on Windows

How to compile, transfer, and run a program on your micro:bit on Firefox for Windows.

While you’re writing and testing your programs, you’ll mostly be running them in the simulator, but once you’ve finished your program you can compile it and run it on your micro:bit.

The basic steps are:

  1. Connect your micro:bit to your computer via USB
  2. Click Download and download the .hex file
  3. Click the Save As button and save the .hex file into the MICROBIT drive


You need the following things to transfer and run a script on your micro:bit:

  • A-Male to Micro USB cable to connect your computer to your micro:bit. This is the same cable that is commonly used to connect a smart phone to a computer.
  • A PC running Windows 7 or later.

Step 1: Connect your micro:bit to your computer

First, connect the micro:bit:

  1. Connect the small end of the USB cable to the micro USB port on your micro:bit.

  2. Connect the other end of the USB cable to a USB port on your computer.

Your computer should recognise your micro:bit as a new drive. On computers running Windows, MICROBIT appears as a drive under Devices and drives. On a Mac it appears as a new drive under Devices.

Step 2: Download your program

  1. Open your project on https://makecode.microbit.org/.
  2. Click Download.
  3. When prompted, choose to save the compiled file onto your computer. The prompt will be different depending on which browser you are using, or whether you are using a Windows computer or a Mac.

Save download file dialog

A window may appear asking whether you want to save or open the .hex file. If it doesn’t, go click on the downloads icon at the top of the browser.

Save file prompt

Click the folder icon and copy the file from the list of downloads to the MICROBIT drive.

Move hex file to MICROBIT drive

Step 3: Transfer the file to your micro:bit

  • The LED on the back of your micro:bit flashes during the transfer (which should only take a few seconds).
  • Once transferred, the code will run automatically on your micro:bit. To rerun your program, press the reset button on the back of your micro:bit. The reset button automatically runs the newest file on the micro:bit.

By copying the script onto the MICROBIT drive, you have programmed it into the flash memory on the micro:bit, which means even after you unplug the micro:bit, your program will still run if the micro:bit is powered by battery.

Transfer problems?

Transfer not working? See some troubleshooting tips.