Google has a mammoth set of computers whose main task is to crawl and fetch all the information available on the internet. In this process, the new and updated websites are crawled regularly. These crawlers are also known as robots, spiders, and bots. The algorithm on which these bots work determines which pages are to be crawled and how often. These bots leverage sitemaps submitted by website owners as well as a list of previously crawled URLs to add newly discovered pages to their list.
Google uses two different crawlers —Primary Crawler and Secondary Crawler. The two simulation crawlers used are mobile crawler and desktop crawler. Both these crawlers i.e. mobile and desktop imitate the users experience on the website on mobile and desktop. The primary crawler for new websites is the mobile crawler, which crawls webpages that haven’t been crawled before. The desktop crawler is used for recrawling, which crawls pages that have already been crawled to see how well pages perform on different devices.