Reddit is an American social news aggregation, web content rating, and discussion website. Registered members submit content to the site such as links, text posts, images, and videos, which are then voted up or down by other members. Posts are organized by subject into user-created boards called "communities" or "subreddits", which cover topics such as news, politics, religion, science, movies, video games, music, books, sports, fitness, cooking, pets, and image-sharing. Submissions with more upvotes appear towards the top of their subreddit and, if they receive enough upvotes, ultimately on the site's front page. Although there are strict rules prohibiting harassment, it still occurs, and Reddit administrators moderate the communities and close or restrict them on occasion. Moderation is also conducted by community-specific moderators, who are not considered Reddit employees. As of September 2021, Reddit ranks as the 19th-most-visited website in the world and 7th most-visited website in the U.S., according to Alexa Internet. About 42–49.3% of its user base comes from the United States, followed by the United Kingdom at 7.9–8.2% and Canada at 5.2–7.8%. Twenty-two percent of U.S. adults aged 18 to 29 years, and 14 percent of U.S. adults aged 30 to 49 years, regularly use Reddit. Reddit was founded by University of Virginia roommates Steve Huffman and Alexis Ohanian, with Aaron Swartz, in 2005. Condé Nast Publications acquired the site in October 2006. In 2011, Reddit became an independent subsidiary of Condé Nast's parent company, Advance Publications. In October 2014, Reddit raised $50 million in a funding round led by Sam Altman and including investors Marc Andreessen, Peter Thiel, Ron Conway, Snoop Dogg, and Jared Leto. Their investment valued the company at $500 million then. In July 2017, Reddit raised $200 million for a $1.8 billion valuation, with Advance Publications remaining the majority stakeholder. In February 2019, a $300 million funding round led by Tencent brought the company's valuation to $3 billion. In August 2021, a $700 million funding round led by Fidelity Investments raised that valuation to over $10 billion.