|"A web crawler is a bot that searches and indexes content on the Internet. Essentially, web crawlers are responsible for understanding the content on a web page so they can retrieve it when an inquiry is made."|
Who runs the web crawlers?
Usually search engines and each has its own algorithm. That's what they use to read websites and figure out if the information on the page answers queries well. The crawler will search and categorize pages once it's told to index them. You can do that by uploading a robots.txt file, and that will signal the robot crawler to index your web pages.
How does a web crawler do what it does?
Web crawlers find URLs and examine the pages. They're pretty good at determining how relevant content is to any given search query. They also figure out how authoritative a page is and prioritize which pages to crawl using that. One factor for determining importance is how many external pages (on other websites) link back to a page. When it considers a page important, it will also return and check for updated content more often.
When your page gets crawled, it defines where it will appear in search results - how it ranks - and crawlers from different search engines have slightly different ways of assessing pages. In short, Crawlers search and index web pages, then they filter out bad content and pay more attention to important material while placing it higher in search results.