Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for de-duplicating electronic content based on comparing metadata. In one aspect, a method includes comparing first metadata associated with a first item of electronic content to second metadata associated with a second item of electronic content, and generating a score based on the comparison. The method also includes establishing that the first and second items of electronic content comprise potentially duplicate content when the score is greater than a predetermined threshold value, and providing information identifying either the first or second items of electronic content for display when establishing that the first and second items of electronic content comprise potentially duplicate content.