Web crawler

Definition

A web crawler is an automated program that follows links and visits pages on the web. Search engines use crawlers to discover pages, while other tools may use crawlers to check links, audit sites, or collect public information.

Why it matters

Crawlers affect how websites are discovered and checked. Understanding them helps developers think about sitemaps, robots rules, page links, and whether important content is visible to automated systems.

Example in VCA

In VCA, learners may meet the idea of crawlers when learning why public pages, internal links, metadata, and sitemaps matter for SEO.

Another Real World Example

A search engine crawler visits pages, follows links, and stores information so those pages can appear in search results.

Common mistakes

Confusing crawling with scraping, even though they often overlap.
Assuming every crawler follows the same rules.
Blocking useful crawlers by mistake.
Letting private pages be discoverable through public links.
Running aggressive crawlers that overload a website.