SEO Glossary Terms: Supplemental Index

Google and other search engines employ more than one index when they crawl websites. As well as the main index, there is a secondary index often referred to as the supplemental index. It is so called because the results of that index are considered supplemental to the results in the primary index for the same search terms. Being consigned to the supplemental index of the search engine can result in very poor rankings and traffic levels.

The supplemental index is like a form of indexing purgatory. A page that appears in the supplemental index has not been blacklisted but it is not deemed worth consideration for the main index for one of a number of reasons. Using practices like duplicate content or offering a page that has no links, both requiring SEO attention, may result in a page or several pages being placed into the supplemental index. Fortunately, it is possible to climb out of the supplemental listings and gain a seat in the main rankings in order to drive traffic to a page.

It is conceivably easier to be ranked in the supplemental index than in the primary one because fewer restraints are placed on pages before they are considered for inclusion. While the spiders that crawl pages for the main index are looking for unique SEO content, for example, the supplementary index will allow duplicate pages to be added to their list and ranked accordingly. In SEO terms, though, this means that your page is highly unlikely to enjoy the benefits of search engine traffic; the ultimate goal of SEO.