In this photo illustration the Twitter account of Elon Musk is seen on a mobile cellphone on April 21. (Photo illustration by Christopher Furlong/Getty Images)
CNN  — 

In the six months since Elon Musk completed his acquisition of Twitter, the billionaire has turned the platform on its head by overhauling how it decides which accounts to verify.

Once given out to authenticate a limited number of accounts from celebrities, government agencies and media organizations, the coveted check mark is now available for purchase through the company’s subscription service, Twitter Blue. The result: more checks and more confusion.

There were at least 550,000 Twitter Blue subscribers as of April 23, just days after Musk stripped all users of legacy blue checks, according to estimates provided to CNN by Travis Brown, a Berlin-based software developer. By comparison, more than 400,000 accounts were verified with the legacy blue checks before the purge.

But with Musk gifting some celebrities with the service, it’s unclear how many are actually paying customers. It’s also unclear how much more Twitter can grow subscriptions, which Musk has made central to his plan to boost Twitter’s revenue.

The change to Twitter’s verification process is just one of many ways Musk has shaken the company’s core after taking the helm of Twitter in October. He eliminated over 80% of its staff and reshaped the site’s policies, drawing criticism for the impact these moves could have on safety and transparency. Many top advertisers have left the platform, and Musk valued it last month at around $20 billion, less than half of what he paid for it.

But one of Musk’s boldest and biggest changes has been Twitter Blue. Touted as the successor to the old verification system, the subscription model lets anyone pay $8 per month for a blue badge and other features, like prioritized rankings in conversations and search.

The blowback has been swift. Twitter Blue has stoked chaos and confusion. The program was initially paused only days after its launch when an account impersonating pharmaceutical company Eli Lilly and Company tweeted “insulin is free now,” causing the stock to nosedive.

More recently, the purge of blue checks has led to a cultural change on the platform. Once a sought-after status symbol, many users find the blue badge is no longer cool. Last week, after the blue check began popping up on famous accounts, celebrities such as Lil Nas X and Chrissy Teigen vehemently denied paying for the service.

Here’s a look back at the rise and fall of Twitter’s blue badge: