Crawling refers to a process of collecting content from a website to an index that can be accessed by the search engine. Crawling is carried out by the crawler which is an application that visits a website, searches for links to the web pages of the website and collects them. Usually, the start- or homepage acts as what is called the seed page. This is where the crawler begins the process of searching links to the pages of the website. When the crawler finds links from a page, it follows them to the other pages the links refer to. Then it follows the links found from the other pages and reiterates this procedure until there are no new links to follow. During this process, all of the links to the pages are collected. In addition to the seed page, the crawler can utilize the links found from a sitemap.