Binary Flasher

Flash custom compiled firmware directly from the browser. Upload your .bin files, set the flash offsets, connect your device, and go — no esptool or software install needed.

Browser Compatibility

Web Serial requires Chrome, Edge, or Opera. Firefox and Safari are not supported.

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Finding Your .bin Files

Arduino IDE

1. Open your sketch and go to Sketch → Export Compiled Binary
2. The .bin files appear in your sketch folder alongside the .ino file
3. You’ll find three files:
   • YourSketch.ino.bootloader.bin
   • YourSketch.ino.partitions.bin
   • YourSketch.ino.bin

PlatformIO

After running pio run, build output is in .pio/build/<env>/:

• bootloader.bin
• partitions.bin
• firmware.bin

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Standard Flash Offsets (ESP32-S3)

File	Offset
Bootloader	0x0
Partition table	0x8000
Application firmware	0x10000
OTA data (if used)	0xD000
SPIFFS/LittleFS (if used)	0x290000

Just flashing new code?

If you’re only updating your application code (not the bootloader or partitions), you only need the main .bin file at offset 0x10000. This is the most common workflow for updating existing firmware.

Merged .bin files — use offset 0x0

Some build systems (and the pre-built tinyCore firmware images on this site) produce a merged binary that includes the bootloader, partition table, and application all combined into a single file, starting at address 0x0.

If you flash a merged .bin at the default 0x10000 offset, the device will fail to boot — you’ll be writing the bootloader into the application partition. Always check whether your binary is a merged image and set the offset to 0x0 accordingly.

You can usually tell from the filename: a file called firmware_merged.bin, combined.bin, or one that’s significantly larger than a normal application binary (typically >300 KB for ESP32-S3) is likely a merged image.

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Troubleshooting

Device not appearing in port picker:

• Make sure you’re holding the BOOT button while clicking Connect (or hold BOOT, press and release RESET, then release BOOT)
• Try a different USB cable — some cables are charge-only
• On Windows, install the CP2102 or CH340 driver if needed

Flash fails with “Failed to initialize”:

• The device isn’t in ROM bootloader mode — hold BOOT while connecting
• Try a lower baud rate (the flasher defaults to the highest supported rate)

“Wrong flash size” error:

• Your firmware was compiled for a different partition scheme. Check your Arduino IDE board settings match the tinyCore configuration.

After flashing, device won’t boot:

• This usually means the bootloader or partition table got corrupted. Re-flash all three files (bootloader + partitions + app) starting fresh.