The Search Engine Blog

The Google supplemental index is dead? It appears so. The four years of supplemental index has officially ended. The supplemental index is where Google put pages that would be less likely to needed in a search. This could occur for many reasons including obscure topic, old information in need up updating or just poor content. It made sense as supplemental results did still appear should a search not return enough results from the primary index. It also should have made things faster for Google.
Now that the supplemental index is officially over, does it mean that Google will treat these pages any differently. Will it now spider that content more regularly instead of rarely as it did in the past? I would bet that Google has something similar in place that it isn’t discussing and is cleverly hiding. The supplemental index just made sense when dealing with such a large volume of data. The ones that hated it where the ones trapped there. Gee….stop your complaining and fix the site?

Official Google Webmaster Central Blog: The Ultimate Fate of Supplemental Results