Twitter has revealed an unusual statistic: of its 271 million active accounts, about 23 million are bots.

Detailed in a Securities and Exchange Commission filing, the automated accounts constituting about 8.5 percent of active Twitter accounts post updates without the aid of a human, CNET reported via Quartz. One example of a bot account is a news service that automatically tweets stories.

The new metrics should reassure investors who have been concerned that ads aren't reaching enough users. According to Twitter, 89 percent of active users are people who are visiting the website or the mobile app, Re/code reported.  

The remaining 11 percent access Twitter through third-party apps, and of those accounts, about 8.5 percent are bot accounts that tweet automatically.

"Historically we tracked and reported in this section all users who accessed Twitter through third-party applications," Twitter said in the SEC filing, as quoted by CNET. "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."

Bot accounts aren't necessarily spam; Twitter estimates that less than 5 percent of its monthly active users are spam accounts.

The social network that relies on 140-character messages has been working to present analytics that represent its true reach, which Twitter says expands much further than its 271 million monthly active accounts.

CEO Dick Costolo has told investors that the site's complete audience could be as much as three times that large, Re/code reported.

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