Facebook code hints that hashtags could be coming to the service

References to hashtags in Facebook’s code suggest the social network could be working on bringing the feature — popular on Twitter, Instagram and Tumblr — to its own platform.

Developer Tom Waddington from Cut Out + Keep, who has discovered a number of unreleased Facebook features in the past, today pointed us to a mention of the word “hashtag” in Facebook’s Javascript SDK. He says this likely for an XFBML hashtag plugin, similar to the hashtag tracking widget Twitter offers developers and publishers.

Another mention is in the live source code for Facebook.com. A reference to “EntstreamHashtagOverlay” links hashtags to Facebook’s hovercard feature. This suggests users will be able to hover over a hashtag to get more information, similar to what they can do for people, apps and pages, as seen below.

Waddington also noticed that Facebook.com/hashtag redirects to Facebook.com, leading us to believe the company could be saving this page for an unreleased feature, otherwise it would lead to a 404 error page.

In March, anonymous sources told the Wall Street Journal, AllThingsD and TechCrunch that Facebook was working to integrate hashtags into its service to help users follow trending topics, search for news and contribute to conversations around a particular issue. That same month, Facebook added a job listing for a data editor to join the consumer communications team “responsible for amplifying the many exciting ways people are using Facebook and connecting with others during global events, holidays and other significant moments in time.”

Shortly after, the company added a multiple listings related to strategic partner development, such as roles focused on entertainment companies and public figures in Brazil and Asia, as well as musicians and athletes in the U.S.  In April, Facebook added a listing for a Public Content Partnerships Analyst to use “quantitative analysis, data mining and the presentation of data to communicate how our partners engage with our product.”

Facebook has not commented on the possibility of hashtags on the platform. Users can already include hashtags in their posts — and many do, often for stylistic reasons — but these do not generate links to more posts with the same hashtags. On other services, hashtags serve to label and group conversations. Although they are most associated with Twitter, they have roots in early Internet chat networks and have more recently taken off on Instagram, which Facebook now owns.

Hashtags could give Facebook users new ways to engage with people and content outside their network of friends. The feature could also lead to better ways of searching posts. With Graph Search, Facebook removed the ability to search public conversations. Hashtag search could replace that and improve Facebook’s existing photo search by letting users tag their contents as they do on Instagram.