An XML sitemap is a file you give to search engines that lists every URL on your site you want indexed, along with optional metadata about each page — when it was last modified, how often it changes, and how important it is relative to other pages. Google and Bing read this file to discover pages they might not find through normal link-following, which is especially valuable for large sites, sites with thin internal linking, or new sites that have not yet earned many external links. A sitemap does not guarantee indexing, but it makes discovery significantly faster and more reliable.

The format Google expects is straightforward: a well-formed XML file with a <urlset> root element, one <url> block per page, and a <loc> tag with the full canonical URL. The optional <lastmod>, <changefreq>, and <priority> tags help Google understand your content calendar and allocate crawl budget — <lastmod> is the most useful of the three because Google actually uses it to prioritise recrawling changed pages. The <priority> tag (0.0 to 1.0) is less useful in practice because Google applies its own signals, but setting your homepage to 1.0 and category pages to 0.8 is harmless and consistent with best practice.

For most modern frameworks and platforms (Next.js, WordPress, Shopify, Hugo), a sitemap is auto-generated. But for custom builds, static sites, or any situation where you need to explicitly control which URLs are included, a generator gives you precise control. Common use cases include creating a sitemap for a new site before the CMS plugin is configured, generating a sitemap for a single-page section of a larger site, auditing which URLs are actually in your current sitemap, or building a supplemental sitemap for a new blog or product section.