Sitemap.xml is an XML file listing a site's URLs, meant to help search engines find pages faster — especially ones with few internal links or that were added recently.
File structure and required tags
Each URL is described by a <url> element with a required child <loc> (the page address) and optional <lastmod>, <changefreq>, and <priority>. The protocol caps a single file at 50,000 URLs and 50 MB uncompressed.
The spec hasn't changed much since 2008
The current sitemaps.org protocol version, 0.90, dates back to the original 2005–2006 release and hasn't seen a major revision since. That stability is part of why the same validation rules — required <loc>, W3C Datetime for <lastmod>, the 50,000/50 MB cap — still apply unchanged almost two decades later.
Multiple sitemaps and sitemap index files
When a site has more URLs than one file allows, a sitemapindex file references several individual sitemap files instead. This is standard practice for large sites with tens of thousands of pages.
What this is for
- Check a sitemap's XML structure before submitting it to Google Search Console.
- Confirm the file doesn't exceed the protocol's URL count or size limits.
- Find broken or duplicate entries in a large sitemap file.
Being listed doesn't mean being indexed
A valid sitemap only tells a crawler where to look — it's a list of candidates, not a command. Google still decides independently whether a URL is worth indexing, based on content quality, duplication, and other signals a validator can't check for you.