In client-side rendering, the server sends a minimal HTML document and the browser executes JavaScript to fetch data and render the full page content. Single-page applications (SPAs) built with React, Vue, or Angular commonly use CSR. While CSR enables highly interactive user experiences, it can create SEO challenges if search engine crawlers struggle to execute JavaScript and index the rendered content. Performance optimization and SSR or pre-rendering fallbacks are often implemented to mitigate these issues.