How A Web Crawler Works – Back To The Basics

A web crawler, also known as a spider, is a software program that systematically browses the internet to index and collect information from websites. Here’s how a web crawler works:

  1. Seed URLs: The web crawler begins with a set of seed URLs, which are typically provided by the search engine or determined by the crawler itself.
  2. Crawling: The web crawler follows each URL to the website and begins to crawl through the website’s pages, starting with the homepage.
  3. Indexing: As the crawler navigates through the website, it collects and indexes the content it finds, such as text, images, and metadata.
  4. Link analysis: The crawler also analyzes the links on the website to determine which pages to crawl next. It follows both internal links within the website and external links to other websites.
  5. Recursion: The crawler continues this process, recursively following links and collecting information until it has crawled all the relevant pages on the website.
  6. Storing: The information collected by the crawler is stored in a database or index, which can be used by search engines to provide relevant results to users.

Some additional points to keep in mind:

  • Crawlers typically follow a set of rules, such as the robots.txt file, which specifies which pages the crawler can and cannot access.
  • Crawlers may prioritize certain pages based on factors such as page authority and freshness.
  • Crawlers may also use various techniques to handle dynamic content, such as JavaScript and AJAX, in order to properly index the content.

In summary, a web crawler is a software program that systematically browses the internet to collect and index information from websites. It follows links and recursively crawls through the website, storing the collected information in a database or index that can be used by search engines.