Reddit Is Working on an Entirely New Front Page Algorithm

Last week, a gunman opened fire and killed nine of his classmates and teachers at an Oregon's Umpqua Community College. The mass shooting instantly became front page news everywhere—except for on Reddit.

The most upvoted post, "Active Shooter Reported at Oregon College," took, by some accounts, more than 12 hours to make its way to the front page, despite having thousands of upvotes on the "News" subreddit. Over the last several weeks, hundreds of redditors have complained that the website's front page has seemed more stagnant, with stories that manage to make it to the front page remaining there for longer than they normally would.

So, has something changed? Or is Reddit's algorithm breaking under the load of an ever-increasing user base?

"Users have been complaining about the front page being stale, and they might be right," Steve Huffman, Reddit's CEO, told me in a phone interview. "I've noticed it too. We didn't change anything, but it feels slower."

"Users have expressed a desire to know what's going on if something big is going down," he added. "In the case of the Oregon shooting, people know it's happening and they come to Reddit to see the conversation. We have to make sure that stuff is present."

In an ask me anything a couple weeks ago, Reddit CTO Marty Weiner said a short-lived bug fix temporarily made the front page stagnant.

"There was a short period of time where we made a change that made the velocity of the front page slower, but we reverted that weeks ago and all algorithms that determine hotness are exactly as they were," he wrote. "Nothing has changed."

That short-lived change "threw everyone's attention to the fact that the front page algorithm is weird right now," Huffman told me. Since then, there have been a handful of posts all around the site calling attention to the stagnation, and comments on popular subreddits have echoed the sentiment. As usual, there are some who buy into the idea that Reddit's administrators and moderators are hand picking certain posts that promote brands to stay on the front page. Others are convinced there's been an algorithm change.

Weiner points to a simpler explanation: Reddit's algorithm is broken.

The way Reddit ranks posts is not simply a matter of upvotes and downvotes. If that were the case, older posts with more upvotes would never be supplanted by new ones. Instead, votes on new posts are given more weight, and upvotes on posts that already have a high score aren't weighed as heavily. In simple terms, the 4,000th upvote on a post isn't as important as the fourth upvote on a post.

This system worked fine for quite a while, but Reddit is now extremely popular, with even casual internet users beginning to vote. What Reddit has seen in recent months is an influx of thousands upon thousands of users who vote on the front page then leave the site, meaning posts are staying higher ranked for longer than they should. That 4,000th upvote isn't as important as the fourth, but if it's getting, say, a few thousand upvotes every few minutes and a lower-ranked post isn't seen at all, it's not going to fade into obscurity for quite some time.

"The number of votes has simply outpaced the hotness algorithm," Huffman said. "I'm 90 percent sure it's as simple as that. The other 10 percent is, maybe there's something else going on."

Michel Billard, an independent web developer who has delved into the Reddit algorithm in the past, told me that Huffman's explanation makes sense, and that the company's public-facing code doesn't point to any change being made.

"When there are more active users on the site, front page posts are more likely to stay there longer since they get more fresh votes regularly keeping it 'relevant' and people tend to upvote already heavily upvoted posts because they see them in their front page, that's just how Reddit works," Billard told me. "That means new posts need a little extra push compared to when there were less users."

Huffman says his development team is working on a small fix, and that an entirely new ranking system may be coming in the future. Because the site is so popular, the team has had to revive an in-house "simulator" that approximates an average day on Reddit. He anticipates a fix coming out in a matter of days or weeks.

"Back in the day, we used to just break the site. Because that didn't go so well last time we tried, we're trying out different algorithms without getting people to go all crazy in real life," he said.

Long term, Huffman says that the Reddit experience may become totally personalized, with posts that you've already clicked on perhaps disappearing from the front page entirely.

"The notion of, 'Hey, I'm coming back and it's stale,' I want that to go away—for my own personal use and the business. I think it'll drive up engagement," he said. "If you're coming back 5-10 times a day, you want to see new content every time. Maybe there'll be this middle ground scenario where, if you ignore the link and come back five times and it's still there, that's Reddit saying 'click the damn link, it's important.'"

"That's a longer project, and it's a function of us hiring new people," he added. "If we had more people, we would do it today."

All of this talk of algorithm deficiencies is a welcome change for the company, who months ago had to deal with a moderator strike, an ugly user revolt that ultimately led to the ousting of former CEO Ellen Pao, and complaints about censorship.

"I tell everyone that when people complain about the front page, it means we're doing our job. Redditors have always complained about the front page—it means we're back at the status quo," Huffman said. "A few months of calm have been good for everybody—even the mood around the office is way better than it was a few months ago."