Oath, the Verizon subsidiary that owns the Yahoo and AOL digital media brands, has announced that as of December 17, all adult content will be banned from the Tumblr blogging site. Any still or moving images displaying real-life human genitals or female nipples and any content—even drawn or computer-generated artwork—depicting any sexual acts will be prohibited.

Genitals and female nipples will only be permitted within the context of breastfeeding, childbirth, and in health-related subjects such as gender confirmation surgery. Written erotica will also remain on the site.

Nowadays, pornography represents a substantial element of Tumblr's content. A 2013 estimate said that around 11 percent of the site's 200,000 most-visited domains were porn, and some 22 percent of inbound links were from adult sites.

Tumblr's relaxed attitude both toward adult content and to copyright infringement—a good proportion of the porn is simply lifted from commercial adult websites—created a safe space for adult content. So a wide range of communities—particularly those poorly represented in broadly heteronormative mainstream porn—took advantage of this atmosphere to publish their own pornography. Present-day Tumblr has substantial LGBT, kink, fetish, and BDSM representation, for example. This encompasses a mix both of the commercial (amateur models promoting their content) and the non-commercial (porn made for fun, for empowerment, for the sheer joy of exhibitionism).

This is not to say that Tumblr has done nothing to limit porn before. Shortly after the site was purchased by Yahoo in 2013, blogs marked as not safe for work were hidden; they only became accessible to Tumblr users logged into their accounts. Such sites were also removed from Tumblr's search listings. Photographs have usually been published without problem, but many producers of adult content have noticed that publishing video to the site has become increasingly hit-and-miss, with pornographic video content routinely being pulled.

Porn has caused issues for Tumblr, too. Earlier this year, Apple removed the Tumblr app from the iOS App Store; this was because child porn had been published on Tumblr, and the filtering system the site uses to prevent such things did not catch it.

Going forward, blogs with adult content will not be destroyed. Tumblr says that their owners are free to continue to use their existing blogs to start publishing permitted content.

Tumblr CEO Jeff D'Onofrio said that the decision was motivated by a desire to make Tumblr a more welcoming platform for publishing, suggesting that the presence of adult content made people uncomfortable to express themselves. In his statement, he appeared indifferent to the communities that will be harmed by this action, saying only that there's "no shortage" of adult sites on the Internet, suggesting that they can fill the space once occupied by Tumblr. While there are now a number of outlets for commercialization of self-produced amateur porn, the community element that Tumblr fostered was unique. For now, it's unclear where these communities will move to.