A sitemap is a discovery aid. It lists URLs you consider worth crawling and, optionally, when each was last modified. Google treats it as a hint, a strong one, but still a hint.
When a sitemap actually helps
- The site is large and internal linking is shallow, so some pages are hard to reach by crawling.
- The site is new and has few external links.
- Pages are rich in media (video, images, news) that benefit from sitemap extensions.
- Content changes often and you want
lastmodto signal freshness.
When it does not
A small, well-linked site gains almost nothing. Listing a URL in a sitemap does not make Google index it, and removing a URL does not remove it from the index.
Rules that break sitemaps quietly
- Maximum 50,000 URLs and 50 MB uncompressed per file, split with a sitemap index above that.
- Only include canonical, indexable URLs. Listing a
noindexor redirected URL sends contradictory signals. lastmodmust be accurate. If every URL updates its timestamp on every build, Google learns to ignore the field entirely.
Alien Road recommends: never generate lastmod from the build date. We see this on almost every site running a static generator: the whole sitemap gets today date on every deploy, the signal becomes worthless, and Google stops using it. Take the timestamp from the content record, or omit the field.