Blogging site Tumblr has come under criticism for recent changes to the way it classifies adult material, including search terms, as the word ‘gay’ is currently classified as not safe for work, and does not return any results using the site’s mobile platform.

Since Yahoo bought the site for $1 billion (£650 million), there has been much speculation around the crackdown on porn on the site, which some reports estimate to make up 10% of the content on the site.

Tumblr CEO David Karp addressed the issue last week, speaking on the Colbert Report, saying site administrators were reluctant to begin classifying certain blogs as ‘adult’.

“We’ve taken a pretty hard line on freedom of speech, supporting our users’ creation, whatever that looks like, and that’s just not something we want to police,” he said.

“When you have somebody like Terry Richardson, or any number of talented photographers, posting tasteful photography, I don’t want to have to go in there and draw the line between this photo and this behind the scenes photo of Lady Gaga and her, uh, her nip.”

Rather than Tumblr identifying not safe for work (NSFW), or adult content, users will now be expected to choose a category for their blog out of NSFW or adult.

If they do not choose one, but continue to post content deemed unsuitable, Tumblr may add the classification to the blog.

Tumblr’s mobile platform, however, blocks searches for ‘#gay’, ‘#lesbian’, or ‘#bisexual’, from returning results.

Karp also addressed this in a post on his blog, saying: “Different app environments have different requirements.” Despite that the word ‘gay’ is filtered, the mobile app is still capable of returning other adult results.

Currently blocked on Tumblr’s mobile platform are the words ‘transsexual’, ‘depression’ and ‘blood’, but some which do return results include ‘boys love’, ‘necrophilia’, and ‘asshole’.