Level: Beginner · Free.
A search engine works in three stages: crawling, indexing and ranking. Crawling is when the search engine’s automated programs, called crawlers or spiders, travel the web by following links from page to page and reading what they find. Indexing is when the search engine stores and organises the information from those pages, like a giant library catalogue, so it can find them again quickly.
Ranking happens when someone types a search. The search engine looks through its index and orders the pages that best match the search, using hundreds of signals to decide the order. The most important signals are relevance, how well the page matches what the person is looking for, and quality, whether the content is accurate, helpful and trustworthy, and whether other reputable sites link to it.
Understanding this process tells you what to focus on. Make your pages easy to crawl by linking to them from your main pages and keeping your site organised. Help the search engine understand each page with a clear title and headings that describe the topic. And earn trust by publishing accurate, original content that answers the searcher’s question better than anything else available. Small improvements in all three areas add up over time.