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Social media site Twitter is trialling longer character limits to help users "easily express themselves".

Twitter currently limits tweets to 140 characters, but has doubled that to 280 characters for a small group of users.

The current character limit was "a major cause of frustration" for some users, the firm said in a blog post.

The firm has been suffering from slowing growth and the shift could be one way for the firm to widen its appeal and attract new users.

"Trying to cram your thoughts into a Tweet - we've all been there, and it's a pain," Twitter product manager Aliza Rosen wrote.

Ms Rosen said the longer character limit was being tested in all languages bar Japanese, Chinese and Korean which she said could convey more information in a single character.

"We understand since many of you have been Tweeting for years, there may be an emotional attachment to 140 characters - we felt it, too.

"But we tried this, saw the power of what it will do, and fell in love with this new, still brief, constraint," she said.

Analysis, Dave Lee, BBC North America technology reporter

With constant concerns over hate speech, propaganda bots, and trolling - you might wonder why Twitter is spending its time worrying about doubling the character limit.

Me too, if I'm honest.

But whatever - Jack Dorsey is right to point out that the 140 limit was only ever a technical limitation owing to the limits of text messages, something the service hasn't had to worry about for a long time.

So why not make it a little longer?

It won't be a dramatic change.

Twitter will hope it increases the engagement and attention times of its users.

Marketers will have more characters with which to get their message across, which might make Twitter a bit more cash.

@DaveLeeBBC

Twitter's founder Jack Dorsey was one of the first to try the new limit out, saying it was "a small change, but a big move for us".

But not all users were convinced. Writer Sarah Kendzior said it was too long.

And The Times journalist Sathnam Sanghera pointed out that US President Donald Trump, famed for his prolific tweeting, could get more characters.

But Twitter said the change could mean people tweet more frequently.

"When people don't have to cram their thoughts into 140 characters and actually have some to spare, we see more people tweeting," Ms Rosen said.