This is a follow up post to How Hacker News ranking algorithm works. This time around I will examine how Reddit's default story and comment rankings work. Reddit's algorithms are fairly simple to understand and to implement and in this post I'll dig deeper into them.

The first part of this post will focus on story ranking, i.e. how are Reddit stories ranked? The second part of this post will focus on comment ranking, which does not use the same ranking as stories (unlike Hacker News), Reddit's comment ranking algorithm is quite interesting and the idea guy behind it is Randall Munroe (the author of xkcd).