Express Sitemap XML Middleware

express-sitemap-xml is an Express.js middleware designed to automatically generate and serve sitemap.xml files based on a dynamic list of URLs provided by an async function. It intelligently handles large sitemaps, automatically splitting them into multiple files and generating a sitemap index (sitemap.xml) when more than 50,000 URLs are present, adhering to the sitemap protocol. The current stable version is 3.1.0, with recent updates indicating active maintenance and feature additions, such as image support and base URL fixes. It differentiates itself by its automatic handling of large sitemaps, caching mechanisms for performance, and a flexible API that can also be used independently of Express for pure sitemap generation. The package calls the URL-fetching function at most once every 24 hours, caching the results to optimize performance for subsequent requests.