Spider / SEO Terms Spider Spider refers to an automated program used by search engines to browse and index content across the internet. Also known as a web crawler or bot, a spider visits websites, reads their content and follows links to discover new pages. The information it gathers is then stored in a search engine’s index, which is used to generate search results when someone enters a query. Spiders are essential to how search engines organize and rank content. When a spider visits a website, it starts by reading the content on the homepage or another entry point. It follows internal links to other pages, collecting data such as page titles, headings, keywords and metadata. It also checks for instructions in the site’s robots.txt file, which tells spiders which pages or directories they are allowed to crawl. If a page is blocked or marked as “noindex,” the spider will skip it or exclude it from the search index. Spiders play a key role in search engine optimization (SEO). They determine which pages are indexed, how often content is updated and how links connect different parts of the web. If your website is not crawlable, it may not appear in search results, even if the content is relevant. To support effective crawling, it is important to maintain clean site architecture, ensure mobile and desktop accessibility, and use descriptive tags and links. Whether you are publishing a blog, running an online store or managing a nonprofit site, making your content easy for spiders to read improves your chances of being found by the right audience.