At a high level, the EdgeRank formula is fairly straightforward. But first, some definitions: every item that shows up in your News Feed is considered an Object. If you have an Object in the News Feed (say, a status update), whenever another user interacts with that Object they’re creating what Facebook calls an Edge, which includes actions like tags and comments.
Each Edge has three components important to Facebook’s algorithm:
First, there’s an affinity score between the viewing user and the item’s creator — if you send your friend a lot of Facebook messages and check their profile often, then you’ll have a higher affinity score for that user than you would, say, an old acquaintance you haven’t spoken to in years.
Second, there’s a weight given to each type of Edge. A comment probably has more importance than a Like, for example.
And finally there’s the most obvious factor — time. The older an Edge is, the less important it becomes.
