What Is Google's Supplemental Index and How to Avoid It?

Google's supplemental index is an additional search engine index that may include some of your website's pages. In this case, users won't see some pages of the site in the SERP. This, of course, negatively affects the promotion of the platform.

The Google database includes the main index and the supplemental one, where the pages that are not important from the search engine's perspective are placed. Google is committed to the quality of search results and in most cases adds only useful, informative, and unique pages to the main index. When search engine algorithms evaluate any page of a site as of little value for the main index, it goes to additional - supplemental results.

If there are pages that fall under this filter, the message "In order to show you the most relevant results, we have omitted some entries very similar to the ones already displayed" is displayed at the end of the main index.

1. Duplicated content - unoriginal text is the main reason why some pages go to supplemental results, since Google operates the Panda filter, which restricts low-quality content. This takes into account duplicates within the site, so all non-unique pages should be disallowed from being indexed in the robots.txt file.
2. Incorrect site structure with more than four levels of nesting for some of the pages.
3. Links to questionable websites - the ones that were filtered or banned by Google.
4. Improper internal linking, resulting in low weight.
5. Low trustworthiness of the entire platform associated with a low-quality link profile - links from suspicious and spammy sites.
6. Texts that are too short or filled with spam, the use of auto-generation and auto-translation, resulting in an unreadable and uninformative page.
7. The subject of the page is very different from the other content.
8. There are no title and description tags or they are not unique.

Pages that fall into the supplemental index are not displayed in the main Google search results and do not attract visitors to the site. Only for very rare queries for which there are no results in the main index, it is possible to display supplemental pages.

Keywords from the keyword list added to such pages will not attract traffic from Google.

If the site has many pages in the supplemental index, this negatively affects the overall ranking of the resource. For successful project promotion, it is important to minimize the number of pages in supplemental search results.

To do so, proceed as follows:

1. Edit content in accordance with recommendations from Google - make it unique, structured, useful, and competent. Work on meta tags - they must be unique and informative as well.
2. Think over the structure of the website so that it has three to four levels of nesting.
3. Use the rel = canonical tag to indicate to the search engine the preferred canonical page for indexing.
4. Disallow unimportant and technical pages (for example, authorization, filter and product sorting pages, system files) from being indexed in the robots.txt file.

In this article, we discussed what Google's Supplemental index is - it's an additional search engine index. These results are displayed right after the main index and can be accessed by clicking the "Show hidden results" link.

Pages in the supplemental index negatively affect promotion and in most cases do not allow traffic to the website.

To remove pages from supplemental results, it's necessary to monitor the quality of content, internal and external links, and ensure that web pages comply with recommendations from Google.