The micro-blogging site said for the three months ending June 30, 23 million of its 271 million monthly active users were bots. The company reports its active user base to the Securities and Exchange Commission on a quarterly basis.
"Historically we tracked and reported in this section all users who accessed Twitter through third-party applications," Twitter said in its SEC filing.
This includes users and power tweeters using Twitter-owned apps like TweetDeck and Twitter for Mac, as well as third-party apps like Flipboard or TweetBot.
"We have reviewed and refined our processes, however, to calculate a new metric that is comprised of only such active users who have used applications with the capability to automatically contact our servers for regular updates where there was no discernible user action involved."
The company said only 11 percent of monthly active users accessed the site through third-party apps or Twitter's API.
After separating the category, Twitter found 8 million monthly active users (3 percent) use TweetDeck or Twitter for Mac, 7 million (2.5 percent) use third-party applications, and 23 million (8.5 percent) are bots.
While not all bot accounts are spam according to the company, the fact that 8.5 percent of users are not clicking on ads or viewing sponsored content is troublesome for the site, which is hoping for mobile advertising to drive its revenues. This information shows that Twitter's user growth in the last year has been slower than earlier reported.
These bots work by either spreading spam or retweeting specific content automatically.