Knowledge Hub

Reflashing the Arduino Uno bootloader

Contributed by CircuitScope · Added 05 Oct 2026 · 1 views

Recover a bricked Uno using another Arduino as ISP.

If sketches won't upload and the bootloader is corrupt, burn a fresh one:

  1. Load the ArduinoISP example onto a second, working Arduino.
  2. Wire it to the target's ICSP header (MISO, MOSI, SCK, RESET, 5V, GND).
  3. In the IDE choose Board: Arduino Uno, Programmer: Arduino as ISP, then Burn Bootloader.
  4. Upload a normal sketch over USB to confirm it's alive again.