Sitemap index files

What it is

A sitemap index is an XML file that lists other sitemap files. Its root element is <sitemapindex> and each child <sitemap> has a <loc> pointing at a child sitemap, with an optional <lastmod>.

<?xml version="1.0" encoding="UTF-8"?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <sitemap>
    <loc>https://example.com/sitemap-articles.xml</loc>
    <lastmod>2026-05-29</lastmod>
  </sitemap>
  <sitemap>
    <loc>https://example.com/sitemap-products.xml</loc>
    <lastmod>2026-05-28</lastmod>
  </sitemap>
  <sitemap>
    <loc>https://example.com/sitemap-images.xml</loc>
    <lastmod>2026-05-29</lastmod>
  </sitemap>
</sitemapindex>

Submit the index URL to Search Console. Crawlers will fetch the index, then each child sitemap, then each URL.

Why it matters

Two reasons to use an index:

1. Scale. A single sitemap is capped at 50,000 URLs and 50 MB uncompressed. Once a site exceeds either, the only standard-compliant option is to split into multiple sitemaps and reference them from an index.
2. Reporting. Search Console reports submitted-vs-indexed counts per sitemap. Splitting by content type (articles, products, categories, images) lets you see at a glance which section has indexing problems instead of one big number for the whole site.

A site with 500 URLs does not need an index. Adding one anyway is harmless but adds a layer of fetching that gains you nothing.

How to implement

Split sitemaps by something meaningful:

• By content type — sitemap-posts.xml, sitemap-pages.xml, sitemap-products.xml.
• By language or region — sitemap-en.xml, sitemap-nl.xml. Pairs well with hreflang.
• By date — sitemap-2025.xml, sitemap-2026.xml for archive-heavy sites.

Rules:

• Up to 50,000 child sitemaps per index, and the index itself is capped at 50 MB uncompressed.
• Every child sitemap must be on the same host as the index, with limited cross-host exceptions.
• <lastmod> on the index entry should reflect the newest <lastmod> inside the child sitemap. This lets crawlers skip refetching unchanged sections.
• Reference the index from robots.txt and submit only the index in Search Console — do not also submit each child individually.

Common mistakes

• Pointing the index at child sitemaps on a different host.
• Stale <lastmod> on the index while the child sitemap has fresh URLs.
• Splitting arbitrarily (sitemap-1, sitemap-2) so the reporting buckets are meaningless.
• Submitting both the index and each child sitemap, causing duplicate reports.

Verification

• Fetch the index URL. Confirm the root element is <sitemapindex> and each child resolves to a valid sitemap.
• Validate against the sitemaps.org XSD.
• In Search Console, confirm the index shows the expected number of child sitemaps and their per-sitemap indexing stats.