An XML sitemap is a file, usually at yoursite.com/sitemap.xml, that lists the pages you want search engines to know about. It does not change how your site looks. It is a delivery note for crawlers: here are my URLs, and here is when each one last changed.
What is inside the file
The format is defined at sitemaps.org and supported by Google, Bing and others. Each page gets a <url> entry containing a <loc> with the full URL and, optionally, <lastmod> with the date it last changed meaningfully. The protocol also defines <changefreq> and <priority>, but Google says it ignores both.
One file may hold at most 50,000 URLs and be at most 50 MB uncompressed. Bigger sites split their URLs across several files and list those in a sitemap index file. There are also extensions for images, videos, news and language alternates.
Submitting a sitemap: a worked example
A dental practice launches a new site with fourteen pages. Their site builder generates /sitemap.xml automatically. To make sure search engines find it, they do two things: add the line Sitemap: https://example-dental.com/sitemap.xml to robots.txt, and submit the same URL in the Sitemaps report of Google Search Console and in Bing Webmaster Tools. A week later Search Console shows "Success" and fourteen discovered URLs. The report also shows how many of those pages made it into the index, which is the number worth watching.
Is it worth the effort?
Google says small, well-linked sites may not need a sitemap at all, and it never guarantees crawling or indexing. It does help new sites with few external links, large sites, and pages that change often, since accurate lastmod dates prompt faster recrawls. Because most platforms create one for free, the practical job is checking it is correct, not building it.
XML sitemap errors to avoid
- Listing URLs you do not want indexed: redirects, 404s, noindex pages or duplicates. It sends mixed signals.
- Non-canonical URLs. Only list the version your canonical tag points to.
- Fake lastmod dates set to today on every page. Google learns to ignore them.
- Mixing hosts or protocols, such as http URLs in an https site's sitemap.
Related terms
- Sitemap: the broader term, including visual and HTML sitemaps.
- Crawling: the process a sitemap feeds URLs into.
- Indexing: the outcome a sitemap can help but not force.
- Google Search Console: where you submit and monitor it.