Its main feature is that it does not filter out, or post warnings to, links with adult content.

ECONOMIST: Shortened web links are convenient, but they come at a price

MetaCert uses a crawling system to automatically label URLS with adult content.

FORBES: Connect

"Tumblr is home to millions of readers and bloggers from a variety of locations, cultures, and backgrounds with different points of view concerning adult-oriented content, " the entry reads, asking users only to make sure to identify such pages as NSFW ("not safe for work") and, of course, not to post anything illegal.

CNN: What you should know about Tumblr