After digging around on a separate problem, I found that avrdude, avr-gcc and some more tools can be found in two different locations:

(1): C:\Program Files\Arduino\hardware

(2): C:\Users\<user>\AppData\Local\Arduino15\packages\arduino

These two folders also both contain similar copies of the hardware directory where all the bootloader hex-files and source code is stored:

(3): C:\Program Files\Arduino\hardware\arduino\avr

(4): C:\Users\<user>\AppData\Local\Arduino15\packages\arduino\hardware\avr\1.6.17

I say similar because the bootloaders\caterina folder in (4) contains quite a few hex-files that are missing in (3).

When burning a bootloader, looking at verbose output from the Arduino IDE reveals that hex-file and executable of avrdude from (2) are used, not (1).

What is the reason for this? My guess would be that location (1) is deprecated, but why choose to put stuff like this into Appdata in the first place?

  • My guess if that 1) if from a previous version. Did you ever update Arduino?
    – Gerben
    Commented Mar 29, 2017 at 10:02
  • @Gerben I just checked by uninstalling Arduino completely and then reinstalling it. The files in (1) are still there.
    – iFreilicht
    Commented Mar 29, 2017 at 10:28

1 Answer 1


Arduino IDE comes with a "platform" (the arduino AVR) in the Arduino\hardware folder.
Then you can add/upgrade platforms with the boards manager.
These will be installed in C:\Users\\AppData\Local\Arduino15\packages.
The reason for this is that Arduino IDE wants to be able to "work out of the box". If they did not deliver the platform inside the installation/zip a "installation finishing" job needs to run after opening the Arduino IDE.

  • 1
    If that was the case, that would mean that location (4) only contained files of additional board packages. But that's not the case. I just reinstalled and it seems like all arduino files are already in (4) as they were before. The additional boards I had installed are missing now.
    – iFreilicht
    Commented Mar 29, 2017 at 10:33
  • Removing the Arduino IDE does not remove the content of C:\Users\\AppData\Local\Arduino15\packages. When you upgrade the avr board they will be in C:\Users\\AppData\Local\Arduino15\packages. and those will be used (arduino IDE only supports 1 version of each platform)
    – jantje
    Commented Mar 29, 2017 at 11:35

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