Robots.txt is a text file with instructions for search engine crawlers. It defines which areas of a website crawler are allowed to search. It is the first document that crawlers open when visiting your site. However, the file does not only control crawling. You can also integrate a link to your sitemap, which gives search engine crawlers an overview of all existing URLs of your domain. The instructions in a robots.txt file have a strong influence on SEO (Search Engine Optimization) as the file allows you to control search robots. However, if user agents are restricted too much by disallow instructions, this has a negative effect on the ranking of your website. You also have to consider that you won’t rank with web pages you have excluded by disallow in robots.txt. If, on the other hand, there are no or hardly any disallow restrictions, it can happen that pages with duplicate content are indexed, which also has a negative effect on the ranking of these pages. By using robots.txt correctly you can ensure that all important parts of your website are crawled by search bots. Consequently, your entire page content is indexed by Google and other search engines.