What Is a Search Engine?
A search engine is a software system that searches a database of web pages and returns results matching a user's query. The most popular search engines are Google (92% market share), Bing (3%), Yahoo (1%), and DuckDuckGo (growing privacy-focused alternative).
How Search Engines Work
Every search engine follows three fundamental steps:
1. Crawling
Search engine bots (like Googlebot) visit web pages by following links. They read the HTML, discover new pages, and revisit existing pages to check for updates. Your robots.txt file controls what bots can access, and your sitemap helps them find all your pages.
2. Indexing
After crawling, the search engine analyses and stores the page content in its index — a massive database of all known web pages. The engine extracts title tags, headings, text content, links, structured data, and more to understand what each page is about.
3. Ranking
When a user searches, the engine retrieves relevant pages from its index and ranks them by quality and relevance. Ranking factors include content quality, backlinks, on-page SEO, page speed, E-E-A-T, and hundreds of other signals.
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Last updated: March 2026