I would like to clean-delete all my Itunes Playlist...but mantaining all my Music. How to do it in a safe way ?.

The safest way to do anything is to back up the computer first.

You can delete playlists one by one. This is tedious if you have many playlists. Deleting playlists will not affect overall library content but you may get warning messages about syncing problems. If you ever see a message asking if you want to remove a media file (you shouldn't) say no.

Another way to delete playlists is to simply delete the library file (iTunes Library.itl). When you next start iTunes it will create a new, blank file and you can re-add media by dragging to the Automatically Add To iTunes folder. This method will re-set play count, date added, and ratings.

If you want to retain all other information but playlists, e.g. date added, ratings, play counts, etc. then create a new playlist folder, move all of your playlists inside this playlist folder, then delete the folder. That should be easier than deleting each playlist one at a time.

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See About the 'Automatically Add to iTunes' folder - Apple Support.

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