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Missing backlinks explained: bug in Google

Context

Recently HitProfs' research led to the detection of a bug in the internet's most scrutinised search engine Google. After webmasters all over the world panicked when Google backlinks seemed to have been reduced by over 50%. HitProfs discovered the true reason why the reported number of backlinks had dropped so drastically. Until then Google had simply counted all backlinks twice. This problem came on top of backlinks that were otherwise missing, due to Google being late with updating them and a change in the selection of which backlinks to show. HitProfs posted it's findings in the Google news forum at WebmasterWorld where the problem was confirmed by Google within a few hours. It had already been fixed. Below you can read the original text as it was posted on WebmasterWorld on 9 May 2003.

The original post

Hi all,

There has been a lot of talk about the reduced number of backlinks in the new 'Dominic' index. Most of the talking is about Yahoo's huge number of backlinks. (I consider 384K a huge number). A lot of members may also have checked their own. But how many of us have actually *counted* their backlinks?

Google usually estimates the number of backlinks (as it does with the main results) and that guess just seems to be more accurate in the new index.

If you check the backlinks for site with a 'reasonable' number of links in the old (April) index, you'll notice that Google actually shows fewer links then it reports. Even if you click the link on the last page of the SERPS to include the omitted 'similar results' the actual number of results shown is less then the reported number. The difference may actually be about 50%!

These are not the low PR links that never show up as those are simply not included into the reported number. I've checked this with other sites with very few incoming links when Google gives exact numbers.

For a particular site Google will only show 21 out of 'about 42' reported backlinks and 381 out of 'about 764' for another site and 72 out of 144 on yet another site. I've even seen 1 backlink out of 'about 2'.

50% of the reported number of backlinks doesn't even exits!

In the new index the respective numbers for these sites are: 20 out of about 24, 276 of about 291, and 71 of about 75.

What I'm saying is that the number of backlinks hasn't been drastically reduced, Google is just learning to count better.

Google found itself in trouble after the so called 'Dominic' update in May 2003, when it changed its regular update routine. Somehow Google didn't include the data it had gathered in its last crawl of the world wide web so new pages and new backlinks didn't show up in the new index. The 'old' data combined with adjustments in the algorithm and repairing the backlink counting bug caused a lot of uproar.

A couple of hours after HitProfs' original post Google employee GoogleGuy confirmed HitProfs' findings.

Next day the 'missing links discussion' was still going on and GoogleGuy had a hard time calming down webmasters.

In the Dutch forum 'Voelspriet' we covered the topic as well: Google in de war (Which translates as "Google confused").