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Term

Crawler (general)

An automated program that systematically visits web pages, reads their content, and follows links — the foundation for search-engine indices, monitoring tools, and AI training data.

Crawler — explained in more detail

A crawler (also spider or bot) starts from a list of known URLs (seed set), loads the HTML response, extracts links from it, and places them into a crawl queue. Robots protocols (robots.txt, <meta robots>, X-Robots-Tag) and user-agent identification let site operators control the behavior.

Crawlers fall roughly into: search-engine crawlers (Googlebot, Bingbot — build indices), AI crawlers (GPTBot, ClaudeBot, PerplexityBot — collect training and answer data), SEO tools (Screaming Frog, AhrefsBot — audit and competitor analysis), and monitoring/scrapers (uptime checks, commercial data extraction).

Example / practical use

When putting a new site live, you can nudge Googlebot via a Sitemap entry in robots.txt and URL submission through Search Console — otherwise organic discovery often takes days to weeks.

A crawler fetches URLs and follows links; a scraper aims at structured data extraction. Indexer is the downstream stage: the crawler supplies raw data; the indexer turns it into a searchable index.

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