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After months of speculation, Twitter has finally set its initial public offering in motion.

Twitter sent out a tweet on its own Twitter account saying that it had "confidentially submitted an S-1 to the SEC for a planned IPO."

A Twitter spokesperson confirmed the tweet but declined to elaborate.

We've confidentially submitted an S-1 to the SEC for a planned IPO. This Tweet does not constitute an offer of any securities for sale. — Twitter (@twitter) September 12, 2013

By "confidentially" submitting the S-1 document to the SEC, Twitter is taking advantage of a provision under the 2012 JOBS Act that lets companies with under $1 billion in annual revenue file its initial documents with the Securities and Exchange Commission confidentially.

"Only after that give and take," said Jay Ritter, a professor of finance at the University of Florida, "if they still want to go public ... is it required to file a public registration that the world can see."

The seven-year-old Twitter, which to date has raised $1.16 billion in venture capital, and which employs more than 2,000 people, has more than 200 million monthly active users. Research firm eMarketer estimates that Twitter will capture 1.85 percent -- or roughly $308 million -- of the $16.65 billion worldwide mobile ad market this year, and should have nearly $1 billion in advertising revenue in 2014.

Assuming all goes smoothly, Ritter expects Twitter will go public in roughly three months. About a month from now, he added, Twitter will likely file its formal registration statement, at which point potential investors can see the details of the business.

Twitter's announcement comes as its closest competitor, Facebook, is at last doing well on Wall Street. In the first months after Facebook's initially disastrous IPO, most thought that Twitter's hopes for going public had sunk with Facebook's stock. But just yesterday, Facebook's stock, on the strength of dramatically improved mobile revenues, hit its all-time high. Indeed, in an interview at TechCrunch Disrupt yesterday, Facebook CEO Mark Zuckerberg said Twitter should not be afraid of going public.

Twitter's IPO fortunes have generally been tied to that of Facebook because of the similarities between the two companies. In a recent report, Pew found that as of May 2013, 72 percent of online U.S. adults use social-networking sites, up from 67 percent in late 2012. Clearly, then, the market for companies like Facebook and Twitter is growing.

Twitter, too, has been preparing for its IPO for quite some time, acquiring companies and making feature decisions geared towards maximizing revenues.

Jennifer Van Grove contributed to this story.