A sitemap index points to sitemaps rather than to pages. Sites need one when they exceed the limit for a single sitemap, which Google sets at 50MB uncompressed or 50,000 URLs, and many smaller sites use one anyway to keep page types apart. You submit the index, and search engines find the sitemaps listed inside it.
Need help with SEO?
Comppound runs SEO and AI search for SaaS companies. We plan what to publish, produce it with AI, and every page passes automated checks, and a person reviews samples and anything high-risk.
- Published to your site and tracked in Search Console
- One person answers for your account
- Plans from $400 a month, terms from 3 months
Format
The index uses the same namespace as a standard sitemap. The required tags are sitemapindex as the root, one sitemap element per file, and a loc child with that file's URL. The lastmod tag is optional.
<?xml version="1.0" encoding="UTF-8"?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
<sitemap>
<loc>https://example.com/sitemaps/blog.xml</loc>
<lastmod>2026-10-01</lastmod>
</sitemap>
<sitemap>
<loc>https://example.com/sitemaps/integrations.xml</loc>
</sitemap>
</sitemapindex>Limits and rules
The rules come from Google's documentation and the sitemaps.org protocol. Lastmod in an index refers to when the sitemap file changed, not to each page inside it.
- An index can hold up to 50,000 loc tags
- Sitemaps.org limits an index to 50MB (52,428,800 bytes), and it can be compressed
- Google lets you submit up to 500 sitemap index files per site in Search Console
- Listed sitemaps must be on the same site as the index, unless cross-site submission is set up
- Google requires listed sitemaps to sit in the same directory as the index or a deeper one
Why split by page type
Separate sitemaps for blog posts, docs and integrations give you a useful diagnostic. Search Console can show how each submitted sitemap is processed, so a problem with one template stands out rather than being lost in one large file.
Example
Splitting a docs-heavy site
Hypothetical developer platform Cindervane had one sitemap mixing marketing pages, blog posts and thousands of reference docs. When indexing dropped, it was hard to see which part was affected.
The team generated separate sitemaps for each section, listed them in one index and submitted that. The reference docs turned out to be the group with the most excluded URLs, which narrowed the investigation quickly.
Common mistakes
Putting the index in a deeper folder than its sitemaps
Google requires each listed sitemap to be in the same directory as the index or below it. An index at /sitemaps/ cannot list a sitemap at the site root.
Setting lastmod to the current time on every build
Google uses lastmod only if it is consistently and verifiably accurate. A value that changes constantly gives it no reason to trust the date.
Frequently Asked Questions
No. A single sitemap works for anything under the limits. An index is still handy if you want separate reporting by section.
No. Submitting the index is enough for search engines to find the sitemaps it lists.
Keep reading
- XML Sitemap: An XML sitemap is a file listing the URLs you want search engines to discover and crawl, optionally with each page's last-modified date.
- HTML Sitemap: An HTML sitemap is an ordinary web page that links to a site's main sections and pages. Unlike an XML sitemap, it is written for people and gives crawlers real links to follow.
- robots.txt: robots.txt is a plain-text file at a site's root that tells crawlers which paths they may or may not request.
- Google Search Console: Google’s free tool for site owners that shows which searches bring up a site, how often it is clicked, and whether Google can crawl and index its pages.
- AMP: AMP is a web framework for building fast-loading pages under strict rules on JavaScript and CSS. Google no longer requires it for the Top Stories carousel.
- Cache-Control: Cache-Control is an HTTP header that tells browsers and CDNs whether and how long to store a response. Good caching makes repeat loads and crawls faster.
- Canonical URL: A canonical URL is the version of a page search engines treat as the main one when several URLs show the same or very similar content.
- Canonicalization: Canonicalization is the process of choosing one preferred URL when several pages have duplicate or very similar content, so search engines know which version to show.
