The feature, which was first proposed in December, is one of a number of changes to the social media platform that the tech billionaire plans to roll out over the coming months after purchasing it for $44 billion last October.
The increase in character length will be only the second time in Twitter’s 17-year history that it has changed the limit, having previously boosted the original 140 limit to 280 in 2017.
Mr Musk explained that the long form tweets would “get the same timeline screen space as other tweets, but you will be able to click for more”.
It is part of a “much larger” user interface overhaul, which will include the ability to swipe between recommended and followed tweets, as well as a bookmark feature that will function as a “silent like” button.
“We will also be adding simple formatting features like bold, underline and font size later this quarter,” he tweeted.
“The goal is to allow people to publish long-form natively on Twitter, rather than forcing them to use another website. Twitter will continue to recommend brevity in tweets.”
The update may bring an end to lengthy Twitter threads, which have become a popular way of sharing longer form content since the functionality was introduced in 2017.
Some Twitter users criticised the latest long form feature, with some claiming that the brevity of tweets distinguishes Twitter from other platforms like Facebook or Medium.
“Twitter content is supposed to be short and to the point; that’s part of its appeal,” wrote fashion blogger Kat Moon. “Tweets aren’t meant to be full blog posts.”
Film critic Noah Gittell wrote: “Anyone who posts a long form tweet is an automatic block.”
Other Twitter users suggested the feature could be a ploy to get people to subscribe to Twitter Blue, an $8 per month premium version of the platform that allows users to edit their tweets – a feature that would be particularly useful for fixing spelling or grammatical errors in lengthy posts.