In the Arduino IDE, the Tools menu can be used to make some board-specific settings like this:

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... such as Processor Version = "Atmega168P", Processor Speed = "16MHz Crystal Resonator" and so on. These end up choosing fuses when burning a bootloader. They may or may not also set constants that influence library behavior, I'm not sure.

What I'd like to know is how such settings stored, as they don't seem to be stored in any file associated with the sketch. And that being the case, they seem to be lost when using different boards or settings for subsequent projects.

So what files store these settings, at least temporarily, and how might one associate those settings more permanently with the project/sketch, so that they are repeatable later?

1 Answer 1


The board settings from Tools menu are stored in the IDE preferences file.

You can open the file from the Preference dialog of the Arduino IDE. The path to the file is shown at the bottom of the dialog and it is clickable.

  • Thanks for that good clue! And do you know of a way to associate those settings permanently with the project/sketch to which they pertain, so they can be repeated later?
    – gwideman
    Commented Feb 5, 2023 at 1:03
  • 1
    @gwideman arduino.stackexchange.com/questions/91305/…
    – Juraj
    Commented Feb 5, 2023 at 4:47
  • 1
    the link to preferences file is missing in IDE 2.0.3
    – Juraj
    Commented Feb 8, 2023 at 12:46

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