The Digg auto bury algorithm has changed

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  • January 8, 2008
Patrick Altoft

Patrick Altoft

Director of Strategy

Most of you will be aware of the infamous Digg auto bury algorithm by now, for the uninitiated it is a system that prevents all stories from certain blacklisted domains from ever becoming popular. The first time I became aware of the algorithm was in late March 2007 when stories from a certain blog of mine were continually being buried for no reason, sometimes identical stories from lesser blogs were made popular the next day.

Before auto bury came into play Digg used to simply ban urls they didn’t want reaching the homepage. Late last February Digg decided that it would be better to let people submit stories from the banned domains again but made sure they were all added to the auto bury blacklist.

In the past the key characteristic of a domain that was auto buried as opposed to buried by real users was that it was buried after only 2 or 3 Diggs. Something that would be highly unlikely to occur purely through natural burying because not enough users would see the content.

To quote a Graywolf article from March 2007:

Certain domains are flagged to be automatically buried and removed from the normal voting system with as little as one vote and within few as few hours of getting in the queue.

This characteristic meant it was easy to detect domains on auto bury – you just did a search for the url with and without the “Include Buried Stories” checkbox ticked. If all your posts were being buried even those with only a couple of Diggs then you were on the auto bury list.

The Change

At the end of November 2007, just before Digg carried out a major redesign, the auto bury algorithm become more sophisticated. Gone was the mass burying of content with only one or two Diggs – content started only being buried when it gained enough Diggs to have a chance at becoming popular.

New domains such as Copyblogger were quietly added to the auto bury blacklist but because only the stories with a chance of becoming popular were being buried not many people noticed (everybody noticed Copyblogger after Brian pointed it out). After all, not every story can hit the front page so it’s common to see one fall just short.

Now a search for a domain on auto bury reveals lots of posts that haven’t been buried whereas before November every single story would have been buried. The only stories that are being buried under the new algorithm are ones that would probably have gone on to become popular.

So, if you have been struggling to get your domain on the front page of Digg since the end of November, now you know why.

The evidence

To highlight the changes that have been made I will use johnchow.com as an example, it’s well known that John is on the auto bury list and he has a following of fans who still submit content to Digg so there are lots of stories to look at. I have tested this with a lot of domains on the auto bury list and all display the same characteristics.

In the first image we can see that there are no non buried stories between 43 days and 156 days old.

John Chow on auto bury

In the second image we can see that in fact there are loads of stories between 43 and 156 days old but they were all buried, even those with only a couple of Diggs. This was the old auto bury algorithm in action

John Chow on auto bury

The next image shows how the new algorithm is behaving, stories within the last 10 days have not been buried by the auto bury algorithm.

John Chow on auto bury

Finally we can see that the only story to be auto buried since the end of November is a good story that had the potential to become popular.

John Chow on auto bury

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