An excellent adjunct to fact-checking news stories by providing evaluation of media sources' "trustworthiness." NewsGuard's operational of definition of trustworthiness is based on nine criteria, with each site evaluated given a full "report card" based on each of those criteria. A summary evaluation is also arrived at, but the individual evaluations are key. The extension has worked fine for me. My main disappointment is NewsGuard's recent announcement that it plans to start charging for access to its evaluations, which have been free until now.

UPDATE 17 Mar 2020: I noticed a surprising number of extreme reviews for NewsGuard, so I scanned the "5s" and "1s" to get a better sense of what was going on. The 5s seem like a typical mix of vague, highly specific, and everything in between. The 1s seem to fll into three groups: 1) disappointment in the extension changing from free to subscription-based (a disappointing fact I noted in my original review); 2) general disappointment that some sites were given better or poorer evaluations than the reviewer felt was justified; and 3) non-specific negative reviews that reasonably may have been posted solely to lower NewsGuard's credibility as a source for evaluating the quality of news websites. This wreaks of an anti-NewsGuard campaign—perhaps started by sites that received negative ratings.

Obviously, I cannot prove whether there is/was a campaign to disparage NewsGuard, but I encourage those who are considering installing the NewsGuard extension to read a core sample of the reviews with 1-star ratings and decide for yourselves. If you are considering paying monthly for this kind of service, which many people can hardly afford, at least get a sense of how reliable the negative NewsGuard reviews seem to be before you decide.