Reddit hot ranking

In reddit's released source a post's score is upvotes minus downvotes ¹. Hot takes log10 of that score's size ², gives it the score's sign, and adds the seconds between the post's creation and a fixed moment in December 2005, divided by 45,000 ³⁴. 45,000 seconds is 12.5 hours, so a post 12.5 hours newer ties one with ten times the net votes. Compare Hacker News ranking, which divides by age instead.

Because of log10, going from 1 to 10 net votes adds as much as going from 100 to 1,000 ¹. A post with a net negative score gets a sign of minus one, so its votes pull it down ². Hot never decays: a post keeps the number it has, and newer posts simply start higher, which is why old posts slide down the list ³.

When the code merged several subreddits into one list, it divided each post's hot by a factor taken from its subreddit's top post ¹². This code is historical: the repository is archived and receives no updates ³, so it shows how hot worked when the code was released, not necessarily how reddit ranks today.