Safari Web Inspector is a built-in tool in the Safari web browser that helps developers analyze and debug web pages. It provides features like inspecting HTML and CSS elements, monitoring network requests, and viewing console messages. This allows developers to understand how their web applications behave and identify any issues. With Safari Web Inspector, users can also edit web page content in real-time, making it easier to test changes without needing to refresh the page. The tool supports various web technologies, including JavaScript, CSS, and HTML, making it a valuable resource for web development and optimization.