A single sitemap file can contain a maximum of 50,000 URLs.
The Sitemaps.org protocol specifies that a single sitemap file must not contain more than 50,000 URLs. This limit applies regardless of the file format (XML, text, etc.).
When a website has more than 50,000 URLs, it must split them across multiple sitemap files and use a sitemap index to reference them all. A sitemap index can reference up to 50,000 individual sitemaps, allowing for a theoretical maximum of 2.5 billion URLs.
In practice, many CMS platforms automatically handle this splitting. WordPress with Yoast SEO, for example, creates a new sitemap file for every 1,000 URLs (a conservative threshold).
SitemapKit's API lets you discover, extract, and parse XML sitemaps from any domain. Get structured JSON data with all sitemap elements including Sitemap URL Limit.