Web crawler

A web crawler, also known as a spider or spiderbot, is a program that automatically explores websites and collects information about their content. Web crawlers are commonly used by search engines to index web pages and gather data that helps them rank the pages in search results.

When a web crawler visits a website, it follows links to other pages on the site and on other websites. It collects information about each page it visits, such as the page title, URL, text content, images, and links to other pages. This information is then stored in a database and used by search engines to create indexes of web pages.

Web crawlers can also be used for other purposes, such as web scraping, data mining, and monitoring changes to websites. However, web crawling can also be used for malicious purposes, such as scraping sensitive information or launching distributed denial-of-service (DDoS) attacks. Therefore, some websites use measures to block or limit web crawlers to protect their content and resources.