What is an XML sitemap?

XML sitemap, explained

A sitemap is a machine-readable list of your important pages. Search engines use it to find URLs they might miss through links alone, and to notice when pages change. Most frameworks can generate one; in Next.js it's a sitemap.ts file in the app folder.

Google's limits are specific: a single sitemap can hold up to 50,000 URLs or 50MB uncompressed. Bigger sites split their URLs across several sitemaps and list those in a sitemap index file. You submit the sitemap in Search Console and reference it from robots.txt with a Sitemap: line.

Two fields cause the most confusion. Google says it ignores <priority> and <changefreq>, so don't spend time tuning them. It does use <lastmod>, but only when it's consistently and verifiably accurate. That means the date should change when the main content, structured data or links change, not when a copyright year or a sidebar changes. Sites that stamp every URL with today's date on each build teach Google to ignore their dates.

A sitemap is also a canonical signal, although a weak one. Only list the URLs you want indexed: canonical, indexable pages that return 200. Leave out redirects, noindexed pages, duplicates and parameter variants. A sitemap full of URLs Google won't index makes the Page indexing report harder to read and wastes crawls.

For a new site, the sitemap matters more than for an old one, because you have few inbound links for crawlers to follow. Split it by page type (blog, product pages, glossary) so you can see indexing rates per section in Search Console.

Why it matters for founders

New products have almost no backlinks, so Google finds pages slowly. A clean sitemap with honest lastmod dates is the cheapest way to get new pages discovered, and splitting it by section shows you which page types Google is indexing.

Example

Your site has 40 marketing pages and 600 programmatic pages. You publish /sitemap.xml as an index pointing to sitemap-pages.xml and sitemap-integrations.xml, each listing only indexable URLs with real modification dates.

Common mistakes

• Setting every lastmod to the build date.
• Including redirected, noindexed or canonicalized-away URLs.
• Treating submission as a promise of indexing. Google still decides page by page.
• Forgetting to update the sitemap when you delete or move pages.