Sitemap Index
01 Definition
Sitemap Index meaning: A master XML file that points to several individual XML sitemaps.
A sitemap index is an XML file that lists other sitemap files instead of listing URLs directly. Large sites use it because one sitemap is limited to 50,000 URLs or 50 MB uncompressed. Search engines read the index, then fetch each child sitemap it references.
Also called
Why it matters
How Sitemap Index fits the work
It lets big websites organize thousands of URLs across many sitemaps under one file, so you can submit a single link and keep crawling coverage tidy.
In context
An online store with 300,000 products built a sitemap index pointing to seven child sitemaps, each holding under 50,000 product URLs.
Practical note
Each child sitemap and the index itself must obey the 50,000 URL and 50 MB limits. Nesting one index inside another is not supported, so keep the structure only one level deep.