A web crawler, also known as a “spider” or “bot,” is a program that automatically navigates through the internet by visiting websites and following links on those sites.

The main purpose of a web crawler is to discover new and updated pages on the internet and add them to a search engine’s index. Once a page is added to the index, the search engine can then display it in search results when users search for relevant keywords.

A web crawler will typically follow links on a page, download the content and then index it, allowing search engines to show that content when a user makes a query. In short, web crawlers are responsible for discovering new content and keeping a search engine’s index up to date.