I have not been doing any Arduino work for about a year. The last time I ran the Arduino IDE was in the previous version of MacOS. Now that I have updated to the latest MacOS Version Catalina (10.15.2) I discovered that the IDE will not compile because the avr-g++ compiler is 32 bit and will not execute on the now 64-bit required MacOS.

So I did the obvious thing. I went to the arduino.cc web site and downloaded the latest version of Arduino IDE thinking that this should solve the problem. I updated to version 1.8.11 of the IDE but the 32-bit problem persisted.

I finally decided that the IDE was updating (new Arduino IDE app) but that the avr toolchain was not being updated. To force this update, I deleted the entire avr toolchain from my ~/Library folder. Now, re-running the IDE is all it took: It discovered the toolchain missing and re-installed and installed with the correct 64 bit binaries (which were part of the new Arduino App all the time).

Perplexing -- why was the toolchain not updated with the install? Is it a requirement to delete the existing toolchain before doing a new install of the Arduino App?

1 Answer 1


The boards packages maintained by Boards Manager and associated tools are installed in .arduino15 folder. The AVR boards package bundled with IDE is only used when there is no AVR boards package version in the .arduino15 folder.

To locate the .arduino15 folder open Preferences in IDE and there at the bottom of the window is displayed the location of the preferences file with full path to .arduino15 folder.

The content of .arduino15 folder is not changed with IDE update.

  • If content is not changed in .arduino15 folder than how is it installed in the first place. I never explicitly installed that folder. It is certain that Arduino app does indeed install it because after deleting the folder a new copy was indeed installed merely by re-running Arduino (rerun, not install).
    – K7PEH
    Commented Jan 31, 2020 at 19:31
  • @K7PEH, of course the folder is created if it doesn't exist and the preferences file is stored there. but boards packages are installed there only if you install them with the Boards Manager in IDE
    – Juraj
    Commented Jan 31, 2020 at 19:36

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