Sitemap Index

A sitemap index is a special sitemap that lists other sitemap files instead of page URLs. Search engines fetch the index first, then fetch each child sitemap it references.

You need an index once a single sitemap would exceed the protocol limits: 50,000 URLs or 50MB uncompressed per file. Large sites split their URLs across many child sitemaps — often grouped by section, content type, or date — and tie them together with one index file. The index itself can reference up to 50,000 sitemaps.

A practical note: submit the index URL to Search Console rather than every child file individually. Search engines will follow the references automatically. Each child sitemap still has to obey the 50,000-URL and 50MB limits on its own.