<sitemapindex>

A sitemap index is the root XML file in a multi-file sitemap setup. Instead of <urlset> entries pointing at pages, it contains <sitemap> entries pointing at other sitemap XML files. Search engines fetch the index first, then crawl each child sitemap.

When you need one

The XML Sitemap protocol limits each individual sitemap file to:

• 50,000 URLs maximum
• 50 MB uncompressed maximum

If either limit is exceeded, the spec requires you split the sitemap into multiple files and reference them from a sitemap index. Most large e-commerce, news, and programmatic SEO sites end up with hundreds of child sitemaps under a single index.

Anatomy

<?xml version="1.0" encoding="UTF-8"?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <sitemap>
    <loc>https://example.com/sitemap-products-1.xml</loc>
    <lastmod>2026-05-15T10:00:00Z</lastmod>
  </sitemap>
  <sitemap>
    <loc>https://example.com/sitemap-products-2.xml</loc>
    <lastmod>2026-05-15T10:00:00Z</lastmod>
  </sitemap>
</sitemapindex>

Each <sitemap> entry must have a <loc>. The <lastmod> is optional but recommended — Google uses it to decide whether to refetch the referenced child sitemap.

Common mistakes

• Nesting indexes. A sitemap index cannot reference another sitemap index. Google rejects nested indexes with "Couldn't process the sitemap" errors. If you'd need more than 50,000 child sitemaps in a single index, submit multiple indexes separately to GSC.
• Mixing <urlset> and <sitemapindex> in one file. They're different schemas; pick one.
• Stale <lastmod> values. If you update a child sitemap but leave the index unchanged, Google won't know to recrawl it. Update the index whenever any child changes.
• Cross-domain children. All child sitemaps must be on the same host as the index. Cross-domain references require cross-domain sitemap verification in GSC.

What SitemapHost does

SitemapHost auto-generates and maintains a sitemap index whenever your URL count exceeds the per-file budget. The index is regenerated on every push so <lastmod> stays accurate, and IndexNow + GSC submissions hit the index URL by default.