B S Detector is a Chrome, Opera, Safari and Edger extension which aims to warn you about "unreliable" news sources, currently only on Facebook.

It scans links in your timeline and checks for references to sites in the B S Detector blacklist, a potentially lengthy process which can slow you down. If there's a match, an alert tells you that "this website is not a reliable news source" and may display a classification to explain why. These include:

 Fake News: Sources that fabricate stories out of whole cloth with the intent of pranking the public.
 Satire: Sources that provide humorous commentary on current events in the form of fake news.
 Extreme Bias: Sources that traffic in political propaganda and gross distortions of fact.
 Conspiracy Theory: Sources that are well-known promoters of kooky conspiracy theories.
 Rumor Mill: Sources that traffic in rumors, innuendo, and unverified claims.
 State News: Sources in repressive states operating under government sanction.
 Junk Science: Sources that promote scientifically dubious claims.
 Hate Group: Sources that actively promote racism, misogyny, homophobia, and other forms of discrimination.

Visit a blacklisted site directly and you'll see a similar alert at the top of the page, but the extension stops there. You don't have to pay attention to its verdict, and can carry on reading any site just as usual.