Search engine

How does a web search engine work?

Google describes three stages, and the pattern applies to other engines too.

1. Crawling. Automated programs called crawlers download text, images and videos from pages found on the web.
2. Indexing. Google analyzes the content and stores it in a large database, the index.
3. Serving results. When someone searches, Google returns information that is relevant to the query. Google says relevance is determined by hundreds of factors, including location, language and device, and that it does not accept payment to rank a site higher.

For SEO this means a page must be found and crawled and then indexed before it can rank. Wikipedia adds that the engine searches its index rather than the live web.

What types exist?

• Index-based engines run their own index, for example Google and Bing.
• Metasearch engines forward queries to other engines and merge the results.
• AI search products such as ChatGPT Search and Perplexity answer questions in generated text. Search Engine Journal treats them as distinct from traditional engines.

Market share

Statcounter Global Stats put Google at about 90 percent of worldwide search engine usage in September 2026 (89.94 percent) and Bing at about 5 percent (5.29 percent). Shares vary by country, device and month.

Example

For the query “weather Hamburg”, the engine searches its index. A crawler loaded the pages in it earlier, and ranking decides the order of the results.

FAQ

What is a search engine? A system that makes web content findable by collecting, storing and ranking pages for queries.

Last updated: October 7, 2026