What Is a Sitemap Index File? When and How to Use One
How a sitemap index groups several sitemaps, when you need one, and how to submit it.
A sitemap index is a file that lists other sitemap files. Instead of one huge sitemap, you have several smaller ones โ for products, categories, blog posts and so on โ and one index that points to all of them. You submit the index, and search engines find the rest.
When you need one
- Size limits โ a single sitemap can hold up to 50,000 URLs and 50 MB uncompressed. Larger sites must split.
- Organisation โ separate sitemaps by content type make it easier to spot indexing problems.
- Separate sources โ when different systems (shop, blog, help centre) each generate their own sitemap.
Many platforms and SEO plugins already create a sitemap index automatically, often at /sitemap_index.xml or /sitemap.xml.
What it looks like
A sitemap index is an XML file with a sitemapindex root element. Inside are sitemap entries, each with a loc (the URL of a child sitemap) and optionally a lastmod date. It does not list pages directly.
How to split sitemaps
- By type:
sitemap-products.xml,sitemap-categories.xml,sitemap-posts.xml,sitemap-pages.xml. - By size:
sitemap-products-1.xml,sitemap-products-2.xmlwhen one type exceeds the limit.
Only include canonical, indexable URLs that return 200 โ no redirects, noindexed pages or duplicates. Create sitemaps with the free XML sitemap generator.
Submitting the index
- Upload the index and child sitemaps to your site.
- In Search Console, open Sitemaps and submit the index URL.
- Add a
Sitemap:line with the index URL to your robots.txt.
Search Console then shows each child sitemap and how many URLs were discovered from it.
Use it for diagnosis
Separate sitemaps let you filter the Page indexing report by sitemap. If product pages are poorly indexed but blog posts are fine, you know where to look. Read what an XML sitemap is and how to check if a page is indexed.
Keep lastmod honest
Only update lastmod when content meaningfully changes. Accurate dates help search engines decide what to recrawl.
A worked example
A store with 80,000 products had one sitemap that silently stopped at 50,000 URLs, so 30,000 products were missing. It switched to a sitemap index with two product sitemaps plus separate ones for categories and blog posts. Search Console then showed all URLs discovered โ and revealed that one product sitemap had many "Crawled โ currently not indexed" pages, which it investigated next. See crawled โ currently not indexed fix.
Keep sitemaps clean
A sitemap is a list of pages you want indexed, so it should only contain those pages. Review it every few months:
- Remove redirected and deleted URLs.
- Remove noindexed pages.
- Remove duplicate parameter URLs.
- Make sure new sections are included.
Clean sitemaps make Search Console's sitemap reports far more useful, because every "not indexed" URL in them is one you actually care about.
Related guides
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Frequently asked questions
Do small sites need a sitemap index?
No, one sitemap is fine โ though many platforms create an index anyway.
Can a sitemap index list another sitemap index?
No. An index should list sitemap files, not other indexes.
What is the sitemap URL limit?
50,000 URLs or 50 MB uncompressed per sitemap file.
Should I submit every child sitemap separately?
Submitting the index is enough.