Use HTTPS: Open this page from GitHub Pages, not as a local file (file://).
No device found: Try a different USB cable or port. Some cables are charge-only.
Failed to open serial port (macOS): Quit Chrome completely, close Arduino IDE / serial monitors, unplug the board, reopen Chrome, plug the board back in, then click Install and select the port that just appeared. On ESP32-S3 boards, choose USB JTAG/serial debug unit (Espressif), not Bluetooth.
Port already in use: Only one app can hold the serial port. Close PlatformIO, screen, minicom, Cursor serial panels, and any other tools, then retry.
Reset port permissions: In Chrome, open chrome://settings/content/serialPorts, remove old entries for this site, then try again.
Device not entering bootloader: Hold BOOT, tap RESET, release BOOT, then click Install immediately.
Flash fails or device won't boot: Confirm you selected the correct firmware for your board.
Before you start
Use Google Chrome or Microsoft Edge on a computer (not a phone or tablet).
Connect your ESP32-S3 board with a USB data cable.
Close the Arduino IDE serial monitor or any other app using the USB port.
Select the firmware we told you to use from the list below.