The company is revealing the information to "clarify who on Twitter is and isn't real", it says.
The filing, made to the Securities and Exchange Commission (SEC) by Twitter, shows that sophisticated algorithms actually run far more accounts that anyone previously imagined – many of which are indistinguishable from human-operated feeds.
This means it's likely some of Twitter's 271 million active users have interacted with a Twitterbot at some point during their time on the site, and many will have followers that are bots designed to generate buzz for a company or product or that have been created solely to increase a user's follower count.
Bots are different to spam accounts, which simply flood users with tweets and links to dubious products. In fact, some bots do the world of Twitter a public service by disseminating public service information. Many news organisations use algorithms to tweet their latest stories for example.
And some are just for fun. Here's our run down of the best Twitter bots:
@Betelgeuse_3 automatically responds with "It's showtime" every time a tweet references 1980s film Beetlejuice.
@EnjoyTheFilm ruins films and TV shows for users who have tweeted that they are watching a particular show by giving away the ending.
@YourMomBot does exactly what you would expect it to. It adds "your mom" to the start of random tweets and tweets them back at the user. Sometimes they work, sometimes they don't.
@allthecheeses finds its genius in its simplicity and simply retweets any tweet with the word "cheese" it.
@RedScareBot brings back the ghost of Senator John McCarthy in Twitter form. If you happen to mention "communism" or "socialism" on the site, this account will tweet back at you with 140-characters of vitriol and call out the "Red Storm Rising".
@horse_ebooks is undoubtedly the most talked about bot on the web, as bloggers and journalists have dissected the account's tweets, and someone has written a book of poems inspired by the account. There's no rhyme or reason to this bot's tweets except an earnest, misguided aim of selling low rent horse-themed e-books.