Definition
sitemap.xml — An XML sitemap is a file listing a site’s important URLs to help search engines discover them.
Quick answer
Include only canonical, indexable URLs returning 200. Up to 50,000 URLs or 50 MB per file; beyond that use a sitemap index. lastmod must reflect real changes.
What matters
- Google uses lastmod only when it is consistently accurate; priority and changefreq are ignored.
- A sitemap does not guarantee indexing — it is a discovery signal.
- For multilingual sites the sitemap can also carry hreflang annotations.
Sources
- Build and submit a sitemap — Google Search Central