Giving users twice the space to voice their thoughts ushers in a new era for the online platform, whose hallmark 140-character cap had encouraged users to craft succinct missives.
"We're expanding the character limit! We want it to be easier and faster for everyone to express themselves," tweeted the site, which started testing an increase to its limit in most languages in early September.
The changes will be rolling out in all languages except Japanese, Korean, and Chinese, in which space limitations have not been an issue, Twitter said.
It is the first time the tweet character cap has been raised since Twitter was founded 11 years ago.
Twitter, which has been lagging behind rival social networks in user growth and struggling to reach profitability, faced a dilemma over the change in that it could alienate longtime users and transform the nature of the service.
Product manager Aliza Rosen said in a blog post that the test showed most people still used 140 characters or fewer, suggesting the fast-moving nature of Twitter will not change.
"Our goal was to make this possible while ensuring we keep the speed and brevity that makes Twitter, Twitter," Rosen said. "We're excited to share we’ve achieved this goal and are rolling the change out to all languages where cramming was an issue."
Rosen noted that in the first few days of the test many people used the full 280-limit because it was new and novel, "but soon after behavior normalized."
As a result, "the brevity of Twitter remained," she said.
While Twitter itself changed the way people communicate in the internet age, doubling the tweet character limit promised to shift it once again, according to Jennifer Grygiel, an assistant professor of communications at Syracuse University.
"It will slow down the speed at which users consume information and will allow for more clarity," Grygiel said.
"This might not be a bad thing during a time when world leaders are making military threats via the platform."
US President Donald Trump favors the platform for making major policy announcements, as well as criticizing allies, taunting opponents and threatening North Korea with destruction.
He sent his inaugural 280-tweet while on South Korea as part of his Asia tour: "Getting ready to make a major speech to the National Assembly here in South Korea, then will be headed to China where I very much look forward to meeting with President Xi who is just off his great political victory."
Glances and Likes
Some users have worried that longer tweets could profoundly change the nature of the one-to-many messaging platform, which is popular with journalists and politicians but has failed to win the mass appeal of rivals like Facebook.
There was also worry that raising the character cap would give blowhards and abusers more room to spout.
"I will gladly give up my extra 140 characters if Twitter will delete Trump's account," author and civil rights commentator DaShanne Stokes said in a tweet fired off from @dashannestokes.
Stokes said Twitter's move gives Trump "a bigger weapon with which to hurt more people."
Twitter, which became a public company in 2013, has never reported a profit, even though it has built a loyal base of celebrities, journalists and political figures, including prolific tweeter Trump.
Twitter co-founder Biz Stone said that longer test tweets got tended to prompt more engagement by others using the service.
"In addition to more Tweeting, people who had 280 characters received more Likes, Retweets, @mentions, Followers, and were more satisfied with Twitter. So, you’ll be getting 280 too -- enjoy!" Stone tweeted.
Some analysts maintain longer tweets are not the fix Twitter needs, and may even change the appealing ability to take in messages with glances.
It also risks Twitter looking a bit more like Facebook, one analyst contended, and might prompt the leading online social network to respond to what it might see as a competitive threat.
Meanwhile, many users welcomed the news and said raising the character cap was long overdue. Some people already resort to long strings of rapid-fire tweets, known as "tweet storms," to string together lengthy comment.
Last month, Twitter reported its loss for the past quarter narrowed as the company suggested it could reach profitability for the first time in the fourth quarter.
The update showed Twitter's monthly active user base rose slightly to 330 million, roughly in line with forecasts.