Checking “all” in iTunes is a useful feature that allows users to quickly select all songs, albums, or playlists in their library. This can be helpful when performing tasks such as copying multiple items to a playlist or deleting a large number of songs.
To check all items in iTunes, simply click the small checkbox located in the upper-left corner of the iTunes window. This will place a checkmark next to every item in the current view. You can then select multiple items by holding down the Shift or Command key while clicking on the desired items.
