Twitter’s impending IPO has many would-be investors asking how the social network will continue growing revenue as a public company. But they may have gotten a hint to the answer earlier than planned: Some users have begun complaining that Twitter’s mobile app is pushing promoted tweets from advertisers directly to their phones’ home screens.

The notifications, first reported by Buzzfeed, came from the cloud storage site Dropbox and looked like promoted tweets, per the users who received them. Promoted tweets, Twitter’s version of advertising, allows companies to send their 140-character messages to targeted demographics. While the site has long allowed advertisers to target users by device, ads typically appear in Twitter’s mobile app — and only when the user opens it. Push notifications, on the other hand, are far more intrusive.

Twitter will make $583 million in advertising revenue this year, research firm eMarketer estimates, and analysts expect that number to keep growing in the future. As The Post’s Hayley Tsukayama reported yesterday, the site ramped up its attention to advertising products over the past year, with a particular focus on mobile. Just this week, Twitter acquired the mobile ad exchange MoPub for $350 million.

Twitter did not immediately respond to requests for comment, but we’ll update when they do.