Mixxx logs debugging information, MIDI/HID/etc. messages it receives and controller mapping files it loads in the
mixxx.log file. When you report a bug or ask for help on the Mixxx forum or IRC channel, please attach your
mixxx.log file to help us help you. This is a plain text file that can be read with any text editor.
%LOCALAPPDATA%\Mixxx\mixxx.logon Vista and up,
%USERPROFILE%\Local Settings\Application Data\Mixxx\mixxx.logon XP and below. (You can just type either of those into the Location bar of a Computer or Folder window, or even under Start → Run… and press Enter.)
mixxx.logunless you've unchecked
Hide extensions for known file typesin the Windows Explorer folder options. Until then it is just
mixxx, the only text file in that location (with a notepad icon.) By default in Windows 7 and up, extensions for known file types are set to hidden. See How to show or hide file name extensions in Windows Explorer.