Orphan articles: the ’dark matter’ of WikipediaWikipedia is the largest platform for open and freely accessible knowledge online yet, in a new study, researchers have found that around 15% of the content is effectively invisible to readers browsing within Wikipedia. They have developed a new tool to help overcome this. With 60 million articles in more than 300 language versions, Wikipedia's available content grows continuously at a rate of around 200 thousand new articles each month.