Tumblr will ban all pornography from its service this month, in a move that will alter how the social network is used and shows an increased desire by major media companies to restrict which content appears on their websites.

Unlike most major websites, the microblogging outlet has always had a tolerant attitude to legal adult material since it was founded in 2007, gaining a reputation as a safe haven for adult-themed artists, sex workers and pornographers. As a result adult material has flooded the service, where it sits alongside other fandoms for everything from Harry Potter to anime.

However, attempts to provide a “safe mode” for younger users have sometimes caused problems. Last month the Tumblr app was removed from Apple’s app store after its filtering system inadvertently allowed some child pornography to appear on the social network.

Tumblr’s chief executive, Jeff D’Onofrio, said that as the site has grown, its responsibilities to “different age groups, demographics, cultures, and mindsets” have increased and it has now decided to remove all adult material from 17 December.

“We spent considerable time weighing the pros and cons of expression in the community that includes adult content. 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,” he said.

“Bottom line: There are no shortage of sites on the internet that feature adult content. We will leave it to them and focus our efforts on creating the most welcoming environment possible for our community.”

Tumblr said all content including photos, videos or gifs that “show real-life human genitals or female-presenting nipples” would be banned, alongside any content that depicts sex acts. The site insisted that it would still allow non-sexualised images of women’s nipples, in situations such as breastfeeding or works of art.

Websites such as Tumblr were founded in a different internet era when the focus was on the right to publish material. They are increasingly having to rethink their policies after years of criticism for being too permissive and having weak moderation, with major companies increasingly concerned about the content their adverts are appearing alongside.

The decision also reflects challenges at Oath, the media business which owns Tumblr in addition to many former assets of Yahoo and AOL such as the Huffington Post.

Oath was founded in a bid to build an online media business that had sufficient scale to challenge Facebook and Google for advertising revenue, but has recently seen the departure of chief executive Tim Armstrong, with its parent company, the US telecoms firm Verizon, taking a closer interest in its activities.