Crawlers, also known as web spiders or bots, are automated programs used by search engines to systematically browse and index webpages. Their primary role is to understand site content, structure, and links so search engines can rank pages accurately and serve relevant results.

When a crawler visits a website, it scans text, metadata, URLs, and internal links to map information and store it in a search database. Well-structured websites with clean navigation, sitemaps, and fast performance offer easier crawling and indexing.

For instance, Googlebot regularly scans e-commerce sites to identify new product pages, updated pricing, or blog content. If a site blocks crawlers accidentally or loads inefficiently, important pages may fail to rank or even appear in search results.