Converting .aax files to .flac with Nix

February 6th, 2026

Here is a script from my nix-config repository that allows me to download .aax files from my Audible library and convert them to .flac files:

(pkgs.writeShellApplication {
  name = "convert-audiobook";

  runtimeInputs = with pkgs; [
    aaxtomp3
    audible-cli
  ];

  text = ''
    if [[ $# -eq 0 ]]; then
      echo "Usage: $(basename "$0") <file>"

      exit 1
    fi

    file="''$1"

    aaxtomp3 \
      --authcode "$(audible activation-bytes)" \
      --flac \
      --single \
      "$file"
  '';
})

Once converted, I can upload and listen to the .flac file within my installation of Audiobookshelf.