Where are 3rd party boards.txt files when downloaded using boards manager?

Suppose I add support for 3rd party boards such as Adafruit's Trinket using boards manager in the IDE, and now I would like to go look at the boards.txt file for Trinket to see what's in it. Does anybody know where that gets downloaded to?

On my Mac the add-on boards are under /Users/username/Library/Arduino15/packages/ On a Windows machine that probably translates to C:\Users\username\AppData\Roaming\Arduino15\packages

Great, thanks! I found the boards.txt file I was looking for on my Mac in ~/Library/Arduino15/packages/adafruit/hardware/avr/1.3.0