In more detail
Each <url> entry has a <loc> and optionally a <lastmod> date; Google has said it ignores <changefreq> and <priority>. One file may hold up to 50,000 URLs or 50 MB uncompressed; larger sites use an index of several sitemaps. List the sitemap's address in robots.txt with a Sitemap: line, or submit it in the search engine's webmaster tools. Only canonical URLs that return 200 belong in it.
Why it matters
A sitemap helps search engines find pages, especially new or poorly linked ones, but it does not guarantee they will be indexed. Listing URLs that redirect, return errors or carry noindex sends mixed signals, and lastmod dates that change on every build teach crawlers to ignore them.
Example
<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
<url>
<loc>https://example.com/guides/dns/</loc>
<lastmod>2026-10-01</lastmod>
</url>
</urlset>
Common confusion
An HTML "site map" page is navigation for visitors; the XML sitemap is a machine-readable list for crawlers.