Microblogging service Tumblr says it is banning pictures of human genitals and female nipples in a bid to create a “better, more positive” experience for its users.

Tumblr CEO Jeff D’Onofrio revealed the changes Monday in a lengthy post published to the platform, saying the company believed banning most forms of graphic sexual content and nudity would make some people feel more comfortable using the service.

“There are no shortage of sites on the internet that feature adult content,” he wrote.

“We will leave it to them and focus our efforts on creating the most welcoming environment possible for our community.”

A separate post provided more details on the ban, which will take effect Dec. 17. Users with existing posts which do not meet the new guidelines will be given advance warning, as well as instruction on how to save their content off-Tumblr or appeal the decision to remove it.

Automated tools will be used to filter through content and flag anything inappropriate, D’Onofrio said, while human moderators will be used to weigh in on situations where additional context is needed, such as nudity at political protests or photographs of Michelangelo’s David.

Exceptions still allowed on Tumblr will include photos of female nipples “in connection with breastfeeding, birth or after-birth moments [or] health-related situations, such as post-mastectomy or gender confirmation surgery.” Nudity in art and sexually explicit written content will also be permitted, although “photorealistic” renditions that could be mistaken for human nudity will not.

“We won’t always get this right, especially in the beginning, but we are determined to make your experience a positive one,” D’Onofrio wrote.

Tumblr, which was purchased by Yahoo for US$1.1 billion in 2013, claims to have nearly 450 million individual microblogs receiving a total of more than 33 million posts per day.

A number of Tumblr users voiced frustrations with the policy change on Tumblr itself, often using the memes and GIFs typically associated with the platform. Others discussed whether users might be willing to move to a new site more accommodating of human nudity.

“Dear Tumblr, we liked you because you were a free place where we could express and show and share anything we felt like,” one user wrote.

“You are killing yourself. You are denying what made us choose you.”