A sitemap is an XML file that lists every URL on a website intended for search engines to index, along with metadata like last modification date and priority. It is the primary mechanism for telling Google and Bing what to crawl.
Sitemaps follow the sitemaps.org protocol and live at any URL, conventionally /sitemap.xml. Large sites split into a sitemap index pointing to multiple sub-sitemaps (max 50,000 URLs or 50 MB each). Each entry can carry `<lastmod>`, `<changefreq>`, and `<priority>`.
Sitemap discovery happens via robots.txt (`Sitemap:` directive), Google Search Console submission, Bing Webmaster Tools, and the IndexNow protocol for instant push notifications.
Without an accurate sitemap, search engines have to discover URLs by crawling internal links — slower, less reliable, and worse for newly published content. Keeping `<lastmod>` accurate is one of the strongest freshness signals in modern SEO.
See it in the product: Sitemap monitoring.