An XML sitemap index is a master file that lists and links to multiple individual XML sitemaps, used when a website is too large for all its URLs to fit within a single sitemap file’s size or URL count limits.
Larger websites, particularly e-commerce sites or publishers with tens of thousands of pages, commonly organize their sitemaps into a sitemap index structure, often separating sitemaps by content type, such as products, categories, and blog posts.
Properly structuring a sitemap index helps search engines efficiently discover and prioritize crawling across a large site’s full range of content, rather than relying on a single, unwieldy sitemap file.
Sitemap index structuring is part of our Technical SEO service for larger websites.