what is the default bootloader of the arduino uno

The default bootloader on the Arduino Uno is Optiboot.

Quick Scoop: Direct Answer

• The official Arduino Uno (ATmega328P-based boards like Uno R2/R3) ships with the Optiboot bootloader preinstalled.

• In the Arduino IDE, when you select Tools → Board → Arduino Uno and choose Burn Bootloader , the file it uses for the Uno is optiboot_atmega328.hex.

Tiny bit of extra context

• Optiboot is a small, space-efficient bootloader that speaks the STK500 protocol used by avrdude and the Arduino IDE for uploading sketches over serial.

• On disk in a typical Arduino installation, the Uno’s bootloader lives under a path like hardware/arduino/avr/bootloaders/optiboot/optiboot_atmega328.hex.

So if you’re ever asked “what is the default bootloader of the Arduino Uno?”, the precise answer is: the Optiboot bootloader for ATmega328P (optiboot_atmega328).

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Find out what the default bootloader of the Arduino Uno is, how it’s identified in the Arduino IDE, and what file (optiboot_atmega328.hex) is used when burning it.

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