NEW YORK (Reuters) - More than 500 news websites have made changes to their standards or disclosures after getting feedback from NewsGuard, a startup that created a credibility ratings system for news on the internet, the company told Reuters this week.

Facebook CEO Mark Zuckerberg is surrounded by members of the media as he arrives to testify before a Senate Judiciary and Commerce Committees joint hearing regarding the company’s use and protection of user data, on Capitol Hill in Washington, U.S., April 10, 2018. REUTERS/Leah Millis TPX IMAGES OF THE DAY

The latest major news organization to work with the company is Britain’s Daily Mail, according to NewsGuard, which upgraded what it calls its “nutrition label” rating on the paper’s site to “green” on Thursday, indicating it “generally maintains basic standards of accuracy and accountability.”

A representative of the Daily Mail did not respond to several requests for comment.

NewsGuard markets itself as an independent arbiter of credible news. It was launched last year by co-chief executives Steven Brill, a veteran U.S. journalist who founded Brill’s Content and the American Lawyer, and Gordon Crovitz, a former publisher of News Corp’s Wall Street Journal.

NewsGuard joins a handful of other groups such as the Trust Project and the Journalism Trust Initiative which aim to help readers discern which sites are credible when many readers have trouble distinguishing fact from fiction.

After facing anger over the rapid spread of false news in the past year or so, Facebook Inc and other tech companies also say they have recruited more human fact checkers to identify and sift out some types of inaccurate articles.

These efforts were prompted at least in part by the 2016 U.S. presidential election, when Facebook and other social media sites were used to disseminate many false news stories.

The company has been criticized by Breitbart News, a politically conservative site, which described NewsGuard as “the establishment media’s latest effort to blacklist alternative media sites.”

The way NewsGuard works is this: red or green shield-shaped labels are visible in a web browser window when looking at a news website if a user downloads NewsGuard’s software from the web. The software is free and works with the four leading browsers: Google’s Chrome, Microsoft Corp’s Edge, Mozilla’s Firefox and Apple Inc’s Safari.

‘CALL EVERYONE FOR COMMENT’

NewsGuard’s investors include the French advertising company Publicis Groupe SA and the non-profit Knight Foundation. Thomas Glocer, the former chief executive of Thomson Reuters, owns a smaller stake, according to NewsGuard’s website. News sites do not pay the company for its service.

The startup said it employs 35 journalists who have reviewed and published labels on about 2,200 sites based on nine journalistic criteria such as whether the site presents information responsibly, has a habit of correcting errors, or discloses its ownership and who is in charge of the content.

News sites field questions if they choose to from NewsGuard journalists about its performance on the nine criteria.

“We call everyone for comment which algorithms don’t do,” Brill said in an interview, highlighting the difference between NewsGuard’s verification process with the computer code used by Alphabet Inc’s Google and Facebook in bringing new stories to the attention of users.

Some news organizations have clarified their ownership, financial backers and identity of their editorial staff after interacting with the company, NewsGuard said.

GateHouse Media, which publishes more than 140 local newspapers such as the Austin American-Statesman and Akron Beacon Journal, made changes to how it identifies sponsored content that may appear to be objective reporting but is actually advertising, after being contacted by NewsGuard.

“We made our standards and practices more prominent and consistent across our digital 460 news brands across the country,” said Jeff Moriarty, GateHouse’s senior vice president of digital.

Reuters News, which earned a green rating on all nine of NewsGuard’s criteria, added the names and titles of its editorial leaders to the Reuters.com website after being contacted by NewsGuard, a Reuters spokesperson said.

NewsGuard upgraded the Daily Mail’s website rating on Thursday to green after giving it a red label in August, when it stated that the site “repeatedly publishes false information and has been forced to pay damages in numerous high-profile cases.”

The Daily Mail objected to that description, and started discussions with NewsGuard in January after the red label became visible for mobile users of Microsoft’s Edge browser, NewsGuard said.

NewsGuard has made public many details of its exchange with the Daily Mail on its website.

“We’re not in the business of trying to give people red marks,” Brill said. “The most common side effect of what we do is for news organizations to improve their journalistic practices.”