Katy Perry was one of the biggest losers in the Great Twitter Follower Purge of 2018, losing about 2.8 million followers overnight.

The pop singer, along with Justin Bieber and former President Barack Obama, led a long list of celebrities, politicians, social media stars and news organizations who saw their followers drop as a result of Twitter's purge of suspicious accounts.

Earlier this week, Twitter said tens of millions of accounts previously locked due to suspicious activity will be removed from its follower counts. The social network said "most" people will lose "four followers or fewer," but prominent Twitter accounts "will experience a more significant drop."

Did they ever.

Social media analytics firm Keyhole tracked the impact of the purge on the 100 most popular Twitter (TWTR) accounts. The list reads like a who's who of US pop culture, with people like Rihanna, Taylor Swift, Kim Kardashian and Oprah collectively losing millions of followers.

Twitter's move to purge locked accounts is part of it's larger effort to safeguard the platform amid heightened scrutiny over the proliferation of trolls, fake news and disinformation on social networks like Twitter and Facebook (FB).

Related: Twitter is purging suspicious accounts from your follower count

President Donald Trump lost 204,000 of his 53.3 million followers.

Singer Justin Bieber lost about 2.7 million followers, while President Obama's total dropped by nearly 2.4 million. That represents almost 2.5% of their respective followers.

New organizations took a hit too. CNN's breaking news account lost roughly 1 million followers, while the main New York Times account lost about 730,000.

Twitter's own account wasn't immune either: It shed more than 12% of its followers, or about 7.8 million users. That made it by far the biggest loser. Company CEO Jack Dorsey tweeted he personally lost 200,000 followers.

Microsoft cofounder and philanthropist Bill Gates lost nearly 900,000 followers, while basketball star LeBron James' follower count dropped by 880,000.

It's long been an open secret that numerous Twitter users rely on bogus accounts and bots to inflate their follower count. Others are unwittingly followed by accounts that have gone dormant. Mounting attention to the issue may have forced the company to address the problem and boost its credibility.

CNNMoney's Seth Fiegerman contributed to this report.