Facebook wants the hashtag.
Facebook is using the mark, most well-known in the Twitterverse, to group conversations, according to the Wall Street Journal. However, don't expect it to show up on your Facebook news feed immediately because the social network is still testing the hashtag, or word or words preceded by #.
The hashtag is probably most associated with Twitter, but that won't stop Facebook from using what has now become synonymous with associating an update or post with a subject. Facebook will use the hashtag to index conversations likely because the hashtag is used a lot on Instagram, which the social network bought last year.