Here are the rules Facebook gives its editors to choose which news stories show up in the 'trending' box

Facebook just posted its internal guidelines for choosing which stories appear in its "Trending" topics section on its right rail. 

The company posted the guidelines in response to a storm of controversy that exploded after a report from Gizmodo quoted former news "curators" who said that the team routinely omitted articles from conservative news sources and could make objective decisions to "inject" stories that weren't actually trending. 

"The guidelines demonstrate that we have a series of checks and balances in place to help surface the most important popular stories, regardless of where they fall on the ideological spectrum," the company's VP of Global Operations writes in a blog post. "Facebook does not allow or advise our reviewers to discriminate against sources of any political origin, period."

Note: These guidelines refer to what is showing up in the Trending section, not on users' News feeds. Here's what that section looks like:

You can read the full document below but here's the rough synopsis:

Potential Trending Topics are first surfaced by an algorithm that identifies topics that have recently spiked in popularity on Facebook (in other words, ones that have a high volume of mentions and a sharp increase in mentions over a short period of time). 

They're then reviewed by the Trending Topics team. The topics are personalized for each user ("via an algorithm that relies on a number of factors, including the importance of the topic, Pages a person has liked, location, feedback provided by the user about previous Trending Topics and what's trending across Facebook overall"). Trending is also integrated into Facebook Search so you can search for any Trending topic that may not show up in your Trending suggestions. 

Here's Facebook's full guidelines for its news curators: