"We want every person around the world to easily express themselves on Twitter, so we're doing something new: we're going to try out a longer limit, 280 characters, in languages impacted by cramming (which is all except Japanese, Chinese, and Korean)."
Right now, only a small group are able to tweet more than 140 characters, and of course, Twitter CEO Jack Dorsey is one of them.
This is a small change, but a big move for us. 140 was an arbitrary choice based on the 160 character SMS limit. Proud of how thoughtful the team has been in solving a real problem people have when trying to tweet. And at the same time maintaining our brevity, speed, and essence! https://t.co/TuHj51MsTu-- jack (@jack) September 26, 2017
More Info: Twitter