A search engine is a system that discovers web pages, stores them in an index and ranks them to answer search queries. Google, Bing and DuckDuckGo are well-known examples.
Why it matters
Search engines are a major source of visitors. They find pages by following links and sitemaps, then rank them using many signals including relevance, quality and performance. A site that is slow, blocked or frequently down can lose visibility.
You can ask search engines which of your pages they have indexed using their webmaster tools, which also report crawl errors and manual actions.
Example
A user types how to renew ssl certificate. The engine looks in its index for matching pages, orders them, and shows titles, URLs and snippets. Your page can only appear if it was crawled and indexed.
Common mistakes
- Assuming a new page is instantly searchable; crawling and indexing take time.
- Blocking crawlers by accident with
robots.txtor anoindextag. - Expecting one fixed ranking; results differ by location, device and personalization.
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