In the broadest sense, the term ‘index’ refers to an organised directory or register that enables quick access to specific information. Its function is to make it possible to efficiently locate and retrieve large amounts of data. You can think of it as a comprehensive library system that precisely catalogues where particular books and articles can be found.
The search engine index
In the field of search engine optimisation (SEO) and performance marketing, the search engine index is of central importance. It is a vast, decentralised database in which search engines such as Google, Bing or DuckDuckGo store billions of web pages that their web crawlers have discovered and analysed. Only content listed in this index can appear in the search results (SERPs) at all. The index thus acts as the source of all potential search results, from which the search engine selects and ranks the most relevant answers to a user’s query.
The indexing process involves several steps: first, search engine bots crawl the internet to find new or updated web pages. The content of these pages is then analysed to understand their relevance, keywords and structure. This extracted information is then stored in the search engine index. This process is dynamic; the index is continuously updated to reflect the constant changes on the internet. An up-to-date and comprehensive index is crucial for the quality and timeliness of search results.
Managing and checking indexing
It is essential for website operators to monitor the indexing status of their content and manage it where necessary. Tools such as Google Search Console provide detailed insights into a website’s index coverage. Here, you can see which pages have been indexed, what issues there are with indexing, and how often Google has visited the page. For example, the message ‘Crawled – not currently indexed’ may mean that, whilst the page is known to Google, it has not (yet) been included in the main index due to quality issues or a lack of relevance.
There are also ways to specifically influence indexing. The use of the noindex-Meta tags in the <head>The `noindex` tag in the `meta` section of an HTML page instructs search engines not to include that specific page in their index. This is useful for pages such as internal search results, shopping basket pages, thank-you pages or test environments that should not appear in public search results. Alternatively, the robots.txtA *.txt file can be used to prevent crawlers from accessing certain directories or files, which indirectly prevents indexing, as the content is not crawled in the first place.
