Twitter has updated its developer rules to ban third-party clients, almost a week after it unceremoniously blocked the apps’ access to its platform, offering almost no explanation to what was going on (via Engadget). The new rules state that you can’t use Twitter’s API or content to “create or attempt to create a substitute or similar service or product to the Twitter Applications.”

The rules, updated on Thursday, make it clear what that means: “Twitter Applications” refers to the company’s “consumer facing products, services, applications, websites, web pages, platforms, and other offerings, including without limitation, those offered via https://twitter.com and Twitter’s mobile applications.” The clause banning alternative services was added to the rules with the most recent update, according to the Wayback Machine.

The rule change comes after Twitter silently broke several popular third-party Twitter clients like Tweetbot and Twitterific starting on January 12th. At the time, the developers behind the apps (many of which have historically shaped the entire Twitter user experience) said they had received no communication whatsoever from the company about what was happening. Then, on January 17th, the company’s developer account tweeted that it was “enforcing its long-standing API rules,” which “may result in some apps not working.”

“We have been respectful of their API rules, as published, for the past 16 years,” wrote Ged Maheux, a co-founder of Twitterific developer The Iconfactory, in a blog post about the app being down. “We have no knowledge that these rules have changed recently or what those changes might be.”

Craig Hockenberry, principal at Iconfactory, put it more bluntly on his personal blog: “There was no advance notice for its creators, customers just got a weird error, and no one is explaining what’s going on. We had no chance to thank customers who have been with us for over a decade. Instead, it’s just another scene in their ongoing shit show.”

Money is likely one of the reasons behind the rule change and third-party client ban. Twitter has been struggling financially since Musk took over, saddling it with billions in debt, and third-party clients likely earn it less money than its first-party one. While some developers pay to access the API, the company doesn’t serve ads through it, reducing its ability to monetize people using alternative apps. It doesn’t help that people using third-party clients may not be as interested in the Twitter Blue subscription service, which mainly adds features to the official Twitter app.

There seemingly hasn’t been any official announcement of the rule change, either from Twitter Dev or Elon Musk. Twitter doesn’t have a communications department to contact.

Correction January 19th, 9:05PM ET: A previous version of this story incorrectly stated that Twitter doesn’t make money off third-party clients, but developers may have to pay to access its API depending on their usage.