Flash firmware from your browser
Flashie lets you flash firmware to ESP32, ESP8266, STM32, and Arduino boards directly from Chrome or Microsoft Edge. No desktop software installation required.
Platform Statistics
Available Projects
4 of 4 projectsFeatured Projects
How to Flash Firmware
Connect your board
Plug your ESP, STM32, or Arduino board into your computer using a USB cable. Make sure the board is recognized by your operating system.
Enter bootloader mode (if needed)
For ESP32: Hold the BOOT button, tap EN, then release BOOT. For STM32: Set BOOT0 to HIGH, BOOT1 to LOW, then press RESET. Arduino boards enter bootloader mode automatically.
Select your project
Browse the available firmware projects on this page and choose the one you want to flash. Check the supported boards list to ensure compatibility.
Click Flash Firmware
Click the green Flash Firmware button on your chosen project. A browser dialog will appear asking you to select the serial port your board is connected to.
Select the serial port
In the dialog, select the serial port (e.g., COM3, /dev/ttyUSB0, /dev/cu.usbserial) and click Connect. The flashing process will begin automatically.
Wait for completion
The firmware will be downloaded and flashed to your board. Do not disconnect the USB cable during this process. Wait for the success message before unplugging.
Important Warnings
Use Chrome or Edge
Firmware flashing requires the Web Serial API, which is only supported in Chrome and Microsoft Edge. Firefox, Safari, and other browsers do not support this feature.
USB cable quality matters
Use a high-quality USB data cable. Some cables are charge-only and won't establish a serial connection. If the port isn't detected, try a different cable.
Bootloader mode is critical
For ESP32 boards, the flash will fail if the board is not in bootloader mode. If you see connection errors, press and hold BOOT, tap EN, and release BOOT before retrying.
Do not disconnect during flashing
Interrupting the flashing process can corrupt the firmware and brick your board. Wait for the success confirmation before disconnecting the USB cable.
HTTPS is required
The Web Serial API only works on secure contexts (HTTPS or localhost). If you're running Flashie locally, use http://localhost. For remote access, HTTPS is mandatory.
Supported Boards
ESP32 Series
ESP32, ESP32-S2, ESP32-S3, ESP32-C3, ESP32-C6
ESP8266 Series
ESP8266, ESP-01, ESP-12, NodeMCU, Wemos D1 Mini
STM32 Series
STM32F103 (Blue Pill), STM32F4 (Black Pill), STM32G0
Arduino Boards
Arduino Uno, Nano, Mega, Leonardo, Micro
Custom Boards
Any board with Web Serial or DFU support can be integrated
Troubleshooting
Failed to download manifest
This error occurs when the manifest.json file cannot be fetched. Verify the manifest URL in your project configuration points to the correct file path. Check that the file exists in the public/projects/<project>/ directory and that GitHub Pages has deployed the latest changes. Clear your browser cache and try again.
Flashing connection failures
Connection failures usually mean the board is not in bootloader mode. For ESP32, hold the BOOT button, press EN, then release BOOT. For ESP8266, connect GPIO0 to GND before powering on. Also check that you selected the correct serial port and that no other program (like Arduino IDE) is using it.
GitHub Pages 404 errors
404 errors on GitHub Pages often indicate incorrect file paths. Ensure your manifest.json path starts with a forward slash and points to the correct location under the public/ folder. Remember that GitHub Pages is case-sensitive. File paths in manifests and firmware references must match exactly.
Incorrect firmware paths
Firmware paths in the manifest.json are relative to the manifest file location. For example, if your manifest is at /projects/my-project/manifest.json and firmware is at /projects/my-project/firmware/firmware.bin, the path in manifest should be firmware/firmware.bin (not absolute).
Browser cache issues
Outdated cache can cause stale manifests or firmware to be served. Perform a hard refresh (Ctrl+F5 or Cmd+Shift+R) to bypass the cache. Alternatively, open DevTools, go to the Network tab, and check 'Disable cache'. For persistent issues, clear all site data in Chrome settings.
USB driver problems
Many ESP32/ESP8266 boards use CH340 or CP2102 USB-to-serial chips. Windows may need drivers: download CH340 drivers or CP2102 drivers from the manufacturer. On macOS and Linux, these usually work out of the box. For STM32 boards, you may need the Zadig tool to install WinUSB drivers for DFU mode.