YouTube, after years of criticism, has finally decided to specifically ban videos that promote the idea that one group is superior to others. The new policy, announced Wednesday, includes a complete prohibition on neo-Nazi content, as well as conspiracy theories denying that certain violent events took place, like the Holocaust and the Sandy Hook school shooting.

The update to YouTube’s hate-speech policy specifically bans videos “alleging that a group is superior in order to justify discrimination, segregation or exclusion based on qualities like age, gender, race, caste, religion, sexual orientation or veteran status,” according to the Google-owned video platform.

With the move, YouTube plans to delete “thousands” of channels and videos, but it didn’t identify any specific ones that will be subject to removal.

Before adopting the outright ban, YouTube has tried to curtail the spread of supremacist video content. In 2017, it began limiting recommendations and features (like comments and the ability to share a video) for supremacist videos. That, according to YouTube, cut views on those videos on average by 80%.

Previously, YouTube has kicked off users espousing extreme views on a case-by-case basis. For example, last year, it banned notorious right-wing conspiracy figure Alex Jones and Infowars from the platform after repeated violations of its community guidelines.

YouTube developed the policy banning supremacist videos with outside groups including the Anti-Defamation League. “While this is an important step forward, this move alone is insufficient and must be followed by many more changes from YouTube and other tech companies to adequately counter the scourge of online hate and extremism,” Jonathan Greenblatt, ADL CEO and national director, said in a statement.

The new YouTube policy “could go a long way toward shutting off the pipeline” of hate speech and harassment but only if enforced appropriately, according to Muslim Advocates’ Madihha Ahussain, special counsel for anti-Muslim bigotry. A critical question, she said, is “how will the company enforce this new policy — especially against popular and profitable YouTubers who espouse anti-Muslim bigotry?”

In addition to the ban on supremacist videos, YouTube said it will expand its systems to limit recommendations of “borderline content and harmful misinformation” — like videos promoting a fake miracle cures or those claiming the Earth is flat — from the U.S. to more countries by the end of 2019. According to the company, since implementing the change in the U.S. in January, views on such videos from recommendations has dropped by over 50%. YouTube also plans to increase its presentation of “authoritative content” in the “watch next” panel for videos that are “close to violating our policies.”

YouTube also said it will more actively enforce its monetization policies to suspend channels that repeatedly “brush up against our hate-speech policies” from the YouTube Partner Program.

The policy change disrupted at least one YouTube channel, News2Share, whose proprietor said he produces coverage documenting extremism. The site demonetized News2Share “within minutes” of the announcement, according to channel operator Ford Fischer. “I am a journalist whose work there is used in dozens of documentaries,” he said in a tweet. YouTube responded that it is investigating the situation.

YouTube noted that some videos that fall into the “supremacist” category could remain on the service if they “discuss topics like pending legislation, aim to condemn or expose hate, or provide analysis of current events.”

“We recognize some of this content has value to researchers and NGOs looking to understand hate in order to combat it, and we are exploring options to make it available to them in the future,” YouTube said in announcing the change.

The updated hate-speech policy to ban neo-Nazi and other extremist content is the latest move by YouTube to clean up the platform. YouTube has tried to balance the goal of providing open expression with the need to eliminate harmful and dangerous information attacking specific groups — an issue that also has plagued social platforms like Facebook and Twitter. Critics have faulted the platform for erring too far on the side of openness, with some alleging YouTube places a higher priority on maximizing views than safety.

This past Monday, YouTube announced additional steps to restrict the possibility that children will be targeted by predators on the service, including banning young kids from live-streaming without adult supervision. That came after YouTube suspended the ability to leave comments on nearly all videos with minors. And in February, YouTube announced that it would demonetize anti-vaccination videos.