The social networking giant said it wanted users to “easily express themselves on Twitter” and believes the current 140-character limit can make it difficult for those “cramming” their tweets in languages such as English and Spanish.
Just 0.4% of tweets sent in Japanese have 140 characters, which is a “considerable difference to a 9% of English tweets having 140 characters”, the company said.
This is due to languages like Japanese and Chinese being able to convey more in one character, it added.
The feature will be available in all languages except Japanese, Chinese and Korean.
The trial is being rolled out to a small percentage of Twitter’s 328 million monthly active users, with the company saying it is “excited to see how those with 280 characters use it”.
Aliza Rosen, Twitter’s product manager said: “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.”
Despite the move to increase character count, Ms Rosen stressed that Twitter was still about brevity, adding: “It’s what makes it such a great way to see what’s happening.
“Tweets get right to the point with the information or thoughts that matter. That is something we will never change.”
Earlier this year, the social media site made all the 140 characters available to users replying to tweets.
It also removed character limits from Direct Messages sent privately between users and stopped counting images and other media attached to tweets as part of the character limit in an attempt to improve the service.
Twitter recorded a 5% increase in the number of users compared with 2016, but revealed in its Q2 earnings this year that revenue fell 5% on the same quarter last year to 574 million dollars (£436 million).