With the proliferation of misinformation through social media, fact-checking has become a critical tool to combat “fake news.” Politifact was one of the fact-checking pioneers, set-up over a decade ago under the Tampa Bay Times in Florida and now housed under the Poynter Institute of Media Studies. We speak to Jon Greenberg, one of its senior correspondents on the process of fact-checking, measuring accuracy via its Truth-O-Meter and the climate of discourse in the US.