Crawling is the process by which search engines discover and download pages on the web using automated programs called crawlers or spiders.
A crawler such as Googlebot starts from a set of known URLs, fetches each one, parses the HTML, and follows the links it finds to discover new URLs, repeating the cycle across the web. Sitemaps and links from other sites feed fresh URLs into the queue. Crawling is the first stage of the search pipeline; it comes before rendering, indexing, and ranking.
For a page to be crawled it must be reachable: linked from somewhere the crawler can reach, not blocked by robots.txt, and served with a successful response code. Crawlers respect robots.txt directives, back off when servers are slow, and prioritize URLs they consider important. A page that cannot be crawled cannot be indexed, which makes crawlability the foundation of technical SEO.
Note the distinction between crawling and indexing. Crawling only means a page was fetched; indexing is the separate decision to store it and make it eligible to appear in results. A page can be crawled and then left out of the index, and a URL blocked from crawling can still be indexed if other pages link to it.
Related: Crawl budget, Robots.txt reference, Indexation check
Claude Vincent is a technical SEO consultant focused on crawlability, rendering, and AI-search visibility. He writes the field guides and case studies at SEO ProCheck, with a bias toward the durable, unglamorous work that decides whether search engines and AI answer engines can actually read and cite a site.
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