The new feature is located at the top of the feed. Fleets can be responded to with an emoji, but the response appears in the form of direct messages, unlike a typical tweet, which can be retweeted or replied to publicly.
Design Director Joshua Harris and Product Manager Sam Haveson said Fleets helps people feel more comfortable.
"Some of you tell us that Tweeting is uncomfortable because it feels so public, so permanent, and like there's so much pressure to rack up Retweets and Likes. That's why, unfortunately, there are so many hot Tweets left in drafts!," says Twitter's blog.
The company also hopes that the new feature will help reduce the pressure around tweets, while users will express random thoughts and feelings.
"Because they disappear from view after a day, fleets helped people feel more comfortable sharing personal and casual thoughts, opinions, and feelings."
The feature will appear in the application on iOS and Android for all users in the coming days. It was first tested in the spring of 2020 in Brazil, and later Fleets appeared in India, Italy, and some other countries.