Twitter is close to agreeing a price for TweetDeck, the add-on application that allows heavy users of the site to track multiple conversations.
Reports in the Wall Street Journal say that people familiar with the matter believed advanced talks had settled on a figure of around $50m (€57m).
TweetDeck allows users to arrange themes in different columns, rather than having to search for them on Twitter.com.
Twitter lets other sites to interact with it directly via an open application programming interface (API), and it is thought that TweetDeck users account for at least one in five of all Tweets.
A Twitter spokesman declined to comment and TweetDeck's chief executive, Iain Dodsworth, didn't respond to requests for comment.
TweetDeck’s website indicates that it has just 15 employees and contractors, although according to the Wall Street Journal it has also been recruiting engineers and others in London and planned to open a UK office this year.
Twitter has increasingly been designing its own applications, so a purchase of TweetDeck would give it access to existing expertise. It already has a close relationship with TweetDeck, thanks to a revenue-sharing agreement over “promoted Tweets”.
Twitter founder Biz Stone has previously said the company will make acquisitions to help it to improve its revenues.
TweetDeck, which has previously been linked with a sale to UberMedia, is available on multiple platforms, including on the iPhone and iPad, as well as a Google Android and Chrome application and on the computer desktop.
It is also popular because it lets users write Tweets longer than Twitter’s 140 character limit.