What’s the difference between Hot and Viral submissions?

The viral section is basically a section of the memes that gain the quickest upvotes. I remember when I first discovered the Latest section, I had a meme that was second from the top and had two upvotes, and that's what I thought "Latest" meant---viral.

Quickest upvotes seems legit. I wonder if a meme can be both Hot and Viral at the same time

Yes they can. For a time yesterday, this one imgflip.com/i/2244x7 was on the top of the front page of Viral and at the bottom of the front page of Hot. Plenty of recent front pagers on Hot are in the Viral pages.

I think most important factor on the Viral pages is number of views per day. I noticed some unsubmitted memes (imgflip meme comments) were on the viral pages the first couple days. Haven't checked to see if those are still on the Viral pages.

Good theory. Does anyone know for sure?

Viral is an interesting category. I've been poking around to see what I can find out. Here are some of my (somewhat dry) observations:

1) Appears that only creations made with the meme generator get ranked on the Viral pages. I dont think creations made with the gif, pie chart or demotivational generators are in there.

2) Appears all memes including unsubmitted meme comments get re-ranked once a day, at midnight Pacific time. The Viral rankings don't change the same way either Hot (upvote and comment activity) or Latest (meme age in days) do.

3) Appears the ranking criteria for the Viral pages are mostly rate of views and how new the meme is, ie views per day, upvotes count somewhat, but not like they do on the Hot pages.

4) There are 10,000 pages of viral memes on imgflip imgflip.com/?sort=viral&;page=10000

5) On high page numbers (like Page 9000) you can only use the back button, to go towards the front of the pile. On each high number page above Page 572, the "next" button at the bottom is grayed out.

That’s interesting. Thanks for the info.