What's the difference between a web crawler and a web spider?
TL;DR
There is no difference between a web crawler and a web spider—they’re two names for the same thing. Both terms refer to automated bots that systematically browse websites by following links and extracting content. The term “spider” comes from how these bots navigate the web of interconnected pages, while “crawler” describes their methodical browsing behavior.
What’s the difference between a web crawler and a web spider?
There is no difference—web crawlers and web spiders are two names for the same technology. Both terms describe automated programs that systematically browse websites by following links and extracting content. “Spider” references navigating the web of interconnected pages, while “crawler” describes methodical browsing behavior. Search engines, APIs, and developers use these terms interchangeably.
Origin of the terms
“Spider” emerged because the internet is called the “web”—and spiders navigate webs. Early search engines like WebCrawler (1994) popularized “crawler.” Both metaphors stuck and remain interchangeable today. Google uses “Googlebot,” Bing uses “Bingbot,” but they’re all crawlers/spiders performing the same function.
Common alternative terms
Other terms for the same technology include “bot” (most generic), “web robot” (older technical literature), and “scraper” (emphasizes data extraction). These all describe overlapping capabilities and are used interchangeably depending on context, though “scraper” sometimes implies more aggressive data collection.
How they work
The process is identical regardless of terminology: start with seed URLs, request and download pages, extract links, add new URLs to the queue, and repeat. Modern crawlers render JavaScript, respect robots.txt, implement rate limiting, and maintain URL frontiers—all the same whether called a crawler or spider.
Why the confusion exists
Different communities adopted different terms—search engines prefer “crawler,” academics use “spider,” security folks say “bot.” Since all these groups work with the same technology, multiple terms entered common usage. Some people try to draw distinctions (spiders only follow links, crawlers scrape content), but these aren’t technically valid—both terms cover the full range of automated web browsing.
Key Takeaways
Web crawlers and web spiders are identical—both terms describe automated programs that browse websites by following links and extracting content. The terms originated from different metaphors but refer to the same technology. Alternative terms like “bot” and “scraper” describe similar capabilities. The terminology choice is just preference—Firecrawl’s crawling service performs the same systematic website traversal whether you call it a crawler, spider, or bot.
data from the web