Most boards with Espressif microcontrollers on circuitpython.org provide a button labelled OPEN INSTALLER. Clicking this button invokes the Web Firmware Installer tool. On boards with full USB support, using this guided tool, you can:

• Erase the flash on a board
• Install CircuitPython
• Fill in settings.toml with your desired network settings.

You can skip some or all of these steps, as needed.

Currently, the OPEN INSTALLER button is only present on the download pages for Espressif boards, but it may be added to other types of boards in the future.

Opening Dialog

To use the Web Firmware installer, first go to https://circuitpython.org/downloads, find the entry for your board, and click on it. You will go to the download page for your particular board.

There will probably be two OPEN INSTALLER buttons on the page, one for the current stable version of CircuitPython, and one for the latest development release. Choose the one you want to use.

When you click OPEN INSTALLER, you will first see the dialog box below. The name of your board will be mentioned in the first paragraph. Read the text if you haven't before, and then click Next.

Installer Menu

The next dialog box you see gives you a menu of choices.

• A Full CircuitPython Install will install install CircuitPython using a BIN file. Then you will then be asked to supply WiFi credentials, which will be written to settings.toml.
• Install CircuitPython BIN only installs CircuitPython, and skips the WiFi credentials step.
• Update WiFi credentials assumes CircuitPython is already installed. It will write the WiFi credentials you enter to settings.toml.

This Guide page describes the Full CircuitPython Install, as shown below. The other choices do less:  Install CircuitPython Bin Only choice stops before updating WiFi credentials, and Update WiFi credentials starts there, skipping the CircuitPython install.

Connect to Your Board

The next dialog box you see will be the one below. Follow the instructions to connect your board to your computer with a data-capable USB cable, and then put the board into ROM bootloader mode.

It is easier to identify the right serial port if you disconnect any other boards or other serial devices.

When you click the Connect button, a dialog box will appear for you to select the serial port. The images below show how this dialog box appears on Windows, macOS, and Linux. Choose the serial port (step 1 in the screenshots), and then click Connect or Select Folder (step 2).

• On Windows, the serial port will be COMnn.
• On Linux, the serial port will usually be something like /dev/ttyACMn, /dev/ttyAMAn, or /dev/ttyUSBn. 
• On macOS, the serial port will be cu.something.

Erase Flash

The next dialog box after Connect to Your Board will ask if you want to erase the flash on your board. In general, don't click Skip Erase, but you can if you are sure you want to preserve the parts of flash that won't get overwritten.

If you choose to erase the flash, you'll see this spinning for a bit:

CircuitPython BIN Installation

Now the installer will download CircuitPython and flash it to the board.

Fill in settings.toml

The last step is to specify network settings. First, the installer will ask you to reconnect to the serial port, so it can send commands to write to CIRCUITPY. Click the Connect button and choose the serial port, as you did above.

Finally, the installer will ask for network settings, and then will write those settings to the settings.toml file on CIRCUITPY. If you don't want to fill in these values now, just close the box, or leave the values blank and click Next.

Done!

Now you're all done!