Binary Flasher

Flash custom firmware without installing anything. Choose your .bin files, set the offsets, connect the board, go. The files never leave your browser — the flasher talks to the chip directly over Web Serial.

Browser support

Web Serial needs Chrome, Edge or Opera on a desktop. Firefox and Safari will not prompt for a port.

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Pre-flight checks

Most failed flashes are addressing mistakes, not bad firmware, so the tool checks the plan before it touches the board:

• Unparseable or unaligned offsets — the ROM loader wants a 4-byte-aligned hex address.
• Two files at the same offset — the second silently overwrites the first.
• Regions that overlap — the tool knows each file’s size, so it can tell when one runs into the next.
• A merged image at 0x10000 — see below. This is the single most common way to end up with a board that will not boot.

Warnings are advisory; errors block the flash until you fix them.

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Finding your .bin files

Arduino IDE

1. Open your sketch, then Sketch → Export Compiled Binary.
2. The files appear beside your .ino:
   • YourSketch.ino.bootloader.bin
   • YourSketch.ino.partitions.bin
   • YourSketch.ino.bin

PlatformIO

After pio run, look in .pio/build/<env>/:

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

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Standard offsets (ESP32-S3)

Region	Offset
Merged image or bootloader	0x0
Partition table	0x8000
OTA data (if used)	0xD000
Application firmware	0x10000
SPIFFS / LittleFS (if used)	0x290000

Just updating your code?

If the bootloader and partition table are already on the board — which they are, unless you have changed the partition scheme — you only need the application image at 0x10000. That is the everyday workflow, and it is what the tool starts on.

Merged images go to 0x0

Some build systems, and the pre-built tinyCore firmware images on this site, produce a merged binary: bootloader, partition table and application combined into one file that starts at 0x0.

Flash a merged image at the default 0x10000 and the board will not boot — you have written the bootloader into the application partition.

The give-aways are the filename (firmware_merged.bin, combined.bin) and the size: anything over about 300 KB on an ESP32-S3 is almost certainly merged. The pre-flight check flags exactly this case.

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Troubleshooting

No device in the port picker

• Hold BOOT while clicking connect — or hold BOOT, tap and release RESET, then release BOOT.
• Try another USB-C cable. Plenty of them are charge-only.
• On Windows, install the CP2102 or CH340 driver if the port never appears.

“Failed to initialize”

The chip is not in ROM bootloader mode. Redo the BOOT/RESET sequence above. If it still fails, try a lower baud rate.

“Wrong flash size”

The firmware was built for a different partition scheme. Check that the board settings in your IDE match the tinyCore configuration.

Flashed fine, but the board won’t boot

Usually a corrupted bootloader or partition table. Re-flash all three regions from scratch — bootloader at 0x0, partitions at 0x8000, application at 0x10000 — or flash a known-good merged image at 0x0.