Bots, also called web crawlers or spiders, are automated software programs that systematically browse the internet to discover, read, and index web pages. Search engines deploy bots to continuously scan the web, collect data about pages, and update their search indexes. Google's primary crawler is called Googlebot, while Bing uses Bingbot and other major search engines have their own equivalents.
How Search Engine Bots Work
Search engine bots begin by crawling a set of known URLs, then follow links on those pages to discover new content. This process — called crawling — runs continuously at massive scale. When a bot visits a page, it downloads the HTML, parses the content, identifies links, and passes all collected data back to the search engine's index. Modern bots can also render JavaScript to access dynamically loaded content. Bots identify themselves through a "user agent" string, which is how websites can recognize and selectively block or allow different crawlers via the robots.txt file.
Types of Bots Relevant to SEO
Different bots serve different purposes in the SEO ecosystem:
- Googlebot: Google's main crawler that indexes web content for Google Search
- Google AdsBot: Crawls landing pages to assess ad quality
- Google Image Bot: Specifically crawls and indexes images
- SEO tool crawlers: Tools like Ahrefs, Semrush, and Screaming Frog use their own bots for auditing
- AI training bots: Crawlers from AI companies that collect training data for language models
Why It Matters for SEO
Bots are the entry point for SEO — if search engine bots cannot crawl your pages, those pages will never be indexed or ranked. Technical SEO is heavily focused on ensuring bots can access, render, and understand your content. Issues like blocked crawling via robots.txt, JavaScript rendering failures, broken links, or crawl budget inefficiencies can prevent important pages from ever appearing in search results, making bot management a foundational SEO concern.