Platformer, a prominent tech newsletter founded by the veteran reporter Casey Newton, is leaving Substack over the company’s failure to police extremist content.

In a post explaining the decision, Newton said his team had identified seven Substack publications “that conveyed explicit support for 1930s German Nazis and called for violence against Jews, among other groups”. He said after weeks of back-and-forth discussions with company leaders about their “laissez-faire approach to content moderation”, he decided to part ways with the platform.

“We didn’t ask Substack to solve racism,” Newton wrote in a post explaining the decision. “We asked it to give us an easy, low-drama place to do business, and to commit to not funding and accelerating the growth of hate movements. Ultimately we did not get either.”

Newton said Platformer would be migrating to Ghost, an open-source newsletter-publishing platform, and would send its next edition through that route as of Tuesday. Whereas Substack recommends newsletters in a feed on a user’s homepage, Ghost does not, acting less as a social network than a technical infrastructure provider. Ghost also does not provide financial support to writers starting new publications, as Substack has in the past.

Controversy around content hosted on Substack has been building after the Atlantic published a story in November claiming the platform “has a Nazi problem”, pointing out that it hosts at least 16 newsletters with overt Nazi symbols. Some of the newsletters cited are subscription-based, earning revenue from which Substack takes 10%.

Following that report, writers behind 247 Substack publications issued an open letter to the company asking it to clarify its policies and explain why it chooses to “promote and allow the monetization of sites that traffic in white nationalism”. In response, the Substack co-founder Hamish McKenzie said the platform would not remove or de-monetize newsletters promoting white nationalism, stating that the platform was “committed to upholding and protecting freedom of expression, even when it hurts”.

That letter was “the moment where I started to think Platformer would need to leave Substack”, Newton writes. “I’m not aware of any major US consumer internet platform that does not explicitly ban praise for Nazi hate speech, much less one that welcomes them to set up shop and start selling subscriptions.” Substack did not respond to a request for comment.

Platformer has been one of the most widely followed newsletters on Substack, amassing more than 170,000 free subscribers since it was launched in October 2020, in addition to paid subscribers. Its success was supported by Substack, which sought to attract traditional journalists to its platform, offering Newton healthcare subsidies and legal support.

Newton stated that Substack had some “compelling advantages” including these benefits as well as the ease of setting up his publication. But those same advantages become a cause for concern when publications benefiting from them disseminate hate, he said.

“The company’s edgelord branding ensures that the fringes will continue to arrive and set up shop, and its infrastructure creates the possibility that those publications will grow quickly,” Newton wrote. “That’s what matters.”