Not to be confused with offline reader. For the search engine of the same name, see WebCrawler.A Web crawler is an Internet bot which systematically browses the World Wide Web, typically for the purpose of Web indexing. A Web crawler may also be called a Web spider, an ant, an automatic indexer, or (in the FOAF software context) a Web scutter.Web search engines and some other sites use Web crawling or spidering software to update their web content or indexes of others sites' web content.