Twitter announces, via tweet, that it has filed for an IPO

Twitter has filed for an initial public offering of stock, months earlier than expected.

The 7-year-old microblogging site announced the news -- via tweet, of course -- on Thursday afternoon: "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."


A minute later, Twitter followed up its IPO tweet with a new message: "Now, back to work" along with a photo of employees in the company's San Francisco offices.

Twitter's valuation has been estimated at about $10 billion.

Under new federal rules, a confidential filing is permitted if a company brings in less than $1 billion in annual revenue.

Thursday's news came as a bit of a surprise, as many tech watchers and analysts hadn't expected the company to file until early 2014 at the earliest.

Research firm EMarketer estimates that Twitter will generate $583 million in advertising sales this year. It's not forecast to cross the $1-billion threshold until 2015, when EMarketer expects Twitter to rake in $1.3 billion in ad revenue.

But more than half of Twitter's revenue already comes from mobile advertising, eliminating one of the main concerns that investors had about Facebook at the time of its IPO.

A Twitter spokesman declined to comment.

Josef Schuster, founder IPO research and investment house IPOX Schuster in Chicago, said now, especially, "is a good time to go public."

"The stock market is doing remarkably well, the economy is good, plenty of capital is available. The stock market is trading at an all time-high," he said. "It's been a very good year for IPO investors."