In the field of Search Engine Optimization (SEO), the term “index” usually refers to the index of a search engine. And since Google is the most important search engine, the term almost always refers to Google’s index. The index of a search engine is a huge database in which billions of URLs are stored. The search engine needs this index to provide users with suitable search results.
Listing in such an index is therefore desirable if you want to generate as much traffic as possible. In the early years of the Internet, there were relatively few opportunities to be included in an index. For many websites, backlinks were the best method at that time. With backlinks, extensive link directories could be created in a short period of time. These link directories gave users an overview of all available topics. DMOZ was considered the most important directory at that time.
Nowadays, link directories are no longer relevant. With the increasing popularity of search engines like Google, the directories have been replaced by special indexes. If you wanted to be considered in search queries, you had to submit your website to the appropriate indexes in the search engine. After submission, the website was crawled by the search engine’s algorithm. During crawling, the algorithm checks the quality and quantity of the content listed on the website.
By now, the algorithm is so effective that it is usually not necessary to register the website with the indexes. In most cases, it is enough to put the website online or share a link to the website on a social network. Google first changed the indexing speed of the algorithm in 2003 to establish a daily update of the index. After that, the index was continuously improved, which means that it can now even be adjusted live in some cases.
