Sitemap Index

A sitemap index is a special XML sitemap that lists other sitemap files instead of listing URLs directly, acting as a master file that groups multiple sitemaps together.

A single XML sitemap has limits: it can hold at most 50,000 URLs and must stay under 50 MB uncompressed. Large sites exceed that easily, so they split their URLs across many sitemap files. A sitemap index ties those files together. You submit the index in Search Console, and the search engine reads it to find every child sitemap, then reads each one to find the URLs.

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

The index file itself follows the same limits, up to 50,000 child sitemaps, which lets a site map millions of URLs in an organized way. Beyond simply staying within size limits, splitting sitemaps by content type, products, articles, categories, makes diagnosis easier: Search Console reports submitted versus indexed counts per sitemap, so you can see which sections of the site have indexing trouble rather than facing one undifferentiated number.

You submit only the index file to Search Console, and the engine handles the rest. Keeping each child sitemap accurate, with current URLs and correct lastmod dates, helps crawlers prioritize what to recrawl.

Related: Robots.txt, Indexation check, Site Architecture