Twitter is at an all-time low just months after co-founder Jack Dorsey took the helm as chief executive officer.
Since its 2013 initial public offering, the company has disappointed investors with slowing user growth and sales. While Dorsey aims to turn it around with product improvements, the moves haven't yet affected the company's numbers.
Twitter shares fell 1.4 percent to $19.98 at the close in New York, their lowest since the company's initial public offering in November 2013.
The stock fell 35 percent in 2015. The decline came after U.S. equity markets suffered their worst week since 2011.
Dorsey said this week that Twitter is looking at new ways to display text, including letting people post longer tweets.
He noted that people are already sharing longer messages by posting screenshots of text, although he added that he expects most tweets to remain "short and sweet and conversational."
The maximum number of characters in a post could be raised to as much as 10,000, a person with knowledge of the matter said, well beyond Twitter's iconic 140-character limit.
Twitter is scheduled to report fourth quarter earnings Feb. 10.