If you logged into Twitter on May 25th and saw a sudden unexpected drop in followers, you were not the only one, as some popular accounts have lost hundreds of thousands mysteriously overnight.
Fluctuations in follower counts aren't necessarily uncommon - with Twitter often clearing up bot accounts, accounts reported for spam or breaking the user agreement - but this is one of the more significant and mysterious irregularities.
According to social media statistics tracking website SocialBlade, almost every active verified Twitter account took a hit, with many large accounts losing over 100,000 in single day.
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The mass unfollowing occurred simultaneously across accounts on Friday May 25th, and as of right now it is entirely unexplained.
The largest dip found so far is on Justin Biebers account - the second most followed on Twitter, which lost over 160,000 followers on May 25th.
Similarly, the number one followed account is singer Katy Perry, who lost just over 110,000.
Other big names and smaller accounts too lost thousands of followers, examples of which you can see below - all data coming from SocialBlade.
Justin Bieber - Down 161,967
Katy Perry - Down 118,333
Real Madrid player Cristiano Ronaldo - Down 73,735
Former US President Barack Obama - Down 48,167
And it wasn't just the A listers, but also members of the gaming community such as YouTuber PewDiePie (down 70,095) and Twitch streamer Tyler "Ninja" Blevins (down 8,820), so it seems to be across the board.
Even Twitter's own account (@Twitter) dropped by 38,668, and YouTube's official account by 68,000 flat.
The most likely cause is Twitter doing a clear out of bot or inactive accounts, responding to spam reports en masse.
It is also possible that they are removing accounts which they have evidence to suggest do not comply with the rules of eligibility, such as people under the age 13 years old, which Twitter do not allow.
If we become aware that a child under 13 has provided us with personal information, we take steps to remove such information and terminate the child's account.
However, neither Twitter nor TwitterSupport have released any public information or reasoning for the massive follower decrease on accounts.