Twitter made another attempt to make users’ tallies of followers more accurate on Friday, subtracting millions of suspicious followers which had reappeared on the social media service since a major purge in July.
Twitter is under pressure to tackle its problem of fake users, which are a turn-off for investors and advertisers and have led to scrutiny from U.S. Congress.
The company made Friday’s move without an announcement. Pop star Katy Perry lost about 861,000 followers, according to social measurement firm Social Blade. Twitter’s own account lost 2.4 million followers.
In July, Twitter said it would stop counting accounts it “locked” as followers, in an effort to make its user data more accurate. At least seven celebrities lost as many as 2 million followers each.
By October, however, many of those accounts appeared to have been unlocked – which can happen after a password reset – and at least two dozen popular users had gained back a third or so of the lost followers, according to data from Russian ad fraud researcher Social Puncher.
Those followers disappeared once again on Friday, Social Puncher said.
Twitter said on Friday that it “discovered a bug where some of these accounts were briefly added back, which led to misleading follower counts” for “very few accounts.”
It said in July that follower counts might change “more regularly” as part of its efforts to “identify and challenge problematic accounts.” The ensuing volatility has caught the attention of prominent users, including U.S. President Donald Trump and Tesla Chief Executive Elon Musk.