Twitter says it plans to join the stock market in the most hotly anticipated flotation since Facebook's last year.

Referring to the official paperwork needed to join the market, thecompany tweeted: "We've confidentially submitted an S-1 to the SEC for a planned [initial public offering]."

Investors value Twitter, founded in 2006 by Jack Dorsey, Biz Stone and Evan Williams, at more than $10bn (£6.3bn).

Twitter gave no further details as to the timing or price of the offering.

The microblogging service is on track to post $583m in revenue in 2013, according to advertising consultancy eMarketer, up from $288m in 2012.

Most of Twitter's funding comes from advertising, with companies paying for "promoted tweets" that appear in users' Twitter feeds.

Advertisers are keen to target Twitter's 200 million active users, who send more than 500 million tweets a day.

Mobile first

But some analysts believe the risk for Twitter post-flotation is that if the drive for greater advertising revenue leads to increased numbers of adverts in and around the site, they could become intrusive and unpopular with users.

"There's a few issues [such as] how many revenue streams can be developed beyond just advertising, the impact of more people accessing the service via smartphones," said Colin Gillis, a New York-based technology specialist at BGC Partners.

Nearly two-thirds of users access Twitter via mobile devices that have traditionally been difficult for advertisers to reach.

This is one reason why Twitter has acquired MoPub, a mobile-focused advertising exchange, for a reported $350m.

"Twitter was more or less a mobile-first platform from the start and so the company built its experience to work relatively well across devices," Clark Fredriksen of eMarketer told the BBC.

"Ultimately, they did a good job of monetising their mobile user base."

Analysis

Twitter's flotation was long expected, but is only likely to increase scrutiny of the company.

In recent months, it has faced criticism for not doing enough to tackle rape threats against prominent women, as well as for not having enough security measures to prevent media accounts from being hijacked. In parts of the Middle East, leaders have also accused it of being a "scourge" and a "threat to national unity" for its role in opposition protests.

The firm will be mindful of the extra scrutiny Facebook endured after its flotation. Twitter users will also be on guard against the idea that pressure from investors could see them made subject to more adverts.

Investors, meanwhile, may be concerned about churn - the idea that people join and then drop out. Innovation may be the answer to that, with Twitter's new music discovery service and ways of viewing conversations with others being possible solutions.

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