What is a sitemap index?
A sitemap index is an XML file that points to other sitemaps instead of listing pages directly. It lets you split a site's URLs into several sitemap files, for example one for posts, one for pages, and one for products, and submit all of them to search engines with a single URL.
The sitemaps protocol limits each sitemap file to 50,000 URLs and 50 MB uncompressed. A sitemap index is how you go past that, and most sites use one even when they are well below the limit, because separate files are easier to diagnose. If you are new to sitemaps, start with XML sitemap.
Format
A sitemap index uses <sitemapindex> as its root and lists each child sitemap in a <sitemap> element:
<?xml version="1.0" encoding="UTF-8"?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
<sitemap>
<loc>https://example.com/sitemap-post.xml</loc>
<lastmod>2026-09-28</lastmod>
</sitemap>
<sitemap>
<loc>https://example.com/sitemap-page.xml</loc>
</sitemap>
</sitemapindex>
<loc> is required. <lastmod> is optional and should reflect when that child sitemap last changed. A sitemap index can list up to 50,000 sitemaps, and it cannot list other sitemap index files: nesting is not supported.
Why split sitemaps
- Diagnostics. Search Console reports discovered URLs per submitted sitemap. If products are not getting indexed, you can check the product sitemap on its own.
- Efficient recrawling. Crawlers can refetch only the child sitemap whose
lastmodchanged. - Special types. Image sitemaps, video, and news sitemaps can sit in the same index next to the regular ones.
- Scale. Large post types are split into pages, such as
sitemap-post.xmlandsitemap-post-2.xml, each under the limit.
Submitting it
Submit only the index URL in Google Search Console and Bing Webmaster Tools; the child sitemaps are discovered from it. Also add it to robots.txt:
Sitemap: https://example.com/sitemap.xml
The sitemap submission guide walks through Search Console step by step.
In WordPress
WordPress core has generated a basic sitemap index at /wp-sitemap.xml since version 5.5. SEO plugins usually replace it with their own. Hydrogen SEO publishes a sitemap index that links to one sitemap per enabled post type and taxonomy, splits large types into pages of 1,000 entries by default, and adds its URL to robots.txt automatically. Optional video and news sitemaps join the same index when switched on. Details are in the XML sitemaps docs, and the sitemap troubleshooting guide covers common errors.
Common questions
Do I need to submit each child sitemap separately?
No. Submit the sitemap index and search engines read the child sitemaps from it. Submitting children as well does no harm but adds clutter.
Can a sitemap index contain URLs of pages?
No. It may only list sitemap files. Page URLs go inside the child sitemaps.
Why does my site have two sitemap indexes?
Usually WordPress core's /wp-sitemap.xml plus one from an SEO plugin. Most SEO plugins disable the core sitemap; if both are live, submit only the one your plugin manages.