Tumblr today announced it will permanently ban “adult content” on its platform starting December 17th, a massive change that will impact the way some communities use the platform. The ban includes “photos, videos, or GIFs that show real-life human genitals or female-presenting nipples, and any illustrations—that depicts sex acts.”

“We spent considerable time weighing the pros and cons of expression in the community that includes adult content,” said Tumblr’s CEO Jeff D’Onofrio in a company blog post. “In doing so, it became clear that without this content we have the opportunity to create a place where more people feel comfortable expressing themselves.”

The move comes just weeks after the Tumblr app was removed from the iOS Apple App Store due to issues related to child pornography on the platform. In the company blog post, D’Onofrio made it clear the microblogging service has always maintained a zero tolerance policy regarding child pornography.

Not included in the ban is content associated with “health-related situations” like exposed female-presenting nipples in connection with breastfeeding, birth or after-birth moments, and surgery. Written erotica or nudity related to political or newsworthy speech and nudity found in art are still permitted.

“We recognize Tumblr is also a place to speak freely about topics like art, sex positivity, your relationships, your sexuality, and your personal journey,”  D’Onofrio said. “We want to make sure that we continue to foster this type of diversity of expression in the community, so our new policy strives to strike a balance.”

Tumblr will begin enforcing this new policy by flagging and removing explicit blogs through automated tools. Blog users with banned content will get advance notice and the chance to appeal the company’s decision.