This tool will automatically analyse your songs and output the estimated key of the song. Nothing but a few clicks is needed to get the key of any song.
The key will be presented both in the standard key notation and the camelot wheel notation. This tool will help you regardless of what notation you prefer.
By using this tool, you have the opinion to save the key as a metadata tag of your audio file. This might be useful for music library softwares. Note that this feature does not work on WAV files.