direct copy from <a href="http://news.ycombinator.com/item?id=4746566" rel="nofollow">http://news.ycombinator.com/item?id=4746566</a><p>According to the link in dmgrow's comment, it's<p><pre><code> Score = (P-1) / (T+2)^G
</code></pre>
where P is the number of votes, T is the time in hours since submission, and G is a power that controls the steepness/rate of decline in ranking, so popularity is decreases exponentially over time. I'm sure that YC-affiliated posts have a different ranking algorithm, considering you can't vote on them.<p>Some other cool algorithms are:<p>del.icio.us / delicious.com 's: ranked by upvotes in the last hour. I like the elegance of this solution a lot :)<p>reddit's "best" feature: compares the rates at which comments are upvoted to generate the probability that a comment is a good one, which is how posts with fewer votes can be ranked better than posts with more votes. It works well, in my opinion.
I think there's more to it than what the other two comments described. No doubt there is human moderation on HN (beyond users flagging submissions I mean), and maybe a list of domains and keywords to keep some stories from ever hitting front page, even when the submission gets a lot of votes in a short amount of time.<p>Who knows what the reasons why they'd keep a story off the front page. The moderation is emo at times, even resorting to hellbanning, slowbanning etc.<p>Slashdot moderation is way better. It's a better overall system over there.