NEW YORK >> Twitter is going public. The short messaging service aptly tweeted on Thursday it has filed confidential documents for an initial public offering of stock.

But the documents are sealed, as Twitter is taking advantage of federal legislation passed last year that allows companies with less than $1 billion in revenue in its last fiscal year to avoid submitting public IPO documents.

San Francisco-based Twitter Inc. posted on its official Twitter account Thursday afternoon that it has "confidentially submitted an S-1 to the SEC for a planned IPO."

The confidentiality will likely help Twitter avoid the public hoopla that surrounded the initial public offerings of other high-profile social networking companies, including Facebook Inc., which went public in May 2012.

Twitter’s IPO has been long expected. The company has been ramping up its advertising products and working to boost ad revenue in preparation.

Most of Twitter’s revenue comes from advertising. Research firm eMarketer estimates that Twitter will make $582.8 million in worldwide ad revenue this year, up from $288.3 million in 2012. By comparison, Facebook had ad revenue of $1.6 billion in the April-June quarter of this year. By 2015, Twitter’s annual ad revenue is expected to hit $1.33 billion.