Understanding Search Engine Crawling and Indexing Basics

Search engine crawling is the process where search engines send automated bots (called crawlers or spiders) to discover new and updated content on the internet by following links from one page to another. This content can include webpages, images, videos, PDFs, and more. Crawling is essentially the discovery phase where the search engine finds URLs to evaluate.

Indexing follows crawling and involves the search engine processing and analysing the content of the discovered pages to understand what they are about. This includes examining textual content, key HTML tags (like <title>), alt attributes on images, videos, metadata, and other technical elements. The search engine then stores this information in a large database called the index, which acts like a digital library of all the content it has found and deemed relevant enough to keep.

During indexing, the search engine also determines if a page is a duplicate or an alternate version of another page and selects a canonical version to represent that content cluster in search results. It collects signals such as page language, geographic relevance, and usability to help decide how and when to show the page in response to user queries.

Not every crawled page is guaranteed to be indexed. Factors that can prevent indexing include low-quality content, robots meta tags that disallow indexing, or website design issues that make crawling difficult.

In summary:

• Crawling: Automated bots discover content by following links.
• Indexing: The discovered content is analysed, processed, and stored in a searchable database.
• Ranking (beyond your question): When a user searches, the engine retrieves and orders indexed pages by relevance.

Understanding these basics helps in optimising websites for better visibility in search engine results by ensuring content is discoverable, indexable, and relevant.