Daily Kos bias rating is Left. As of May 2017, a large majority of the nearly 1,200 AllSides users who voted on Daily Kos's bias agreed with this rating. According to the Daily Kos website, it has the largest audience in liberal media. In November of 2016, the Daily Kos had 18.5 million unique visitors and more than 80 million page views. Wikipedia refers to Daily Kos as a "group blog and Internet forum focused on liberal American politics," and the Daily Kos website refers to itself as "the largest progressive community site in the United States," further backing up its Left bias rating.
More on Daily Kos
Daily Kos was founded in 2002 by Markos Moulitsas Zúniga, and it received its name from the last syllable of his first name Kos, which was also his nickname in the military. Moulitsas is also a founder of Vox Media. Daily Kos is blog-based, with a large following and often thousands of comments on controversial posts or "open threads." Daily Kos also has a large following on social media and via the Daily Kos email list.