Sitemap.xml Validator & Inspector

No — everything happens in your browser, no network calls. The validator only parses the XML you provide and checks it against the Sitemaps 0.9 spec. To verify that the URLs themselves are reachable, use a separate crawler or curl -I.

Because priority is relative within your own sitemap, not absolute. If every URL is 1.0, it's the same as if none had priority at all — the field carries zero information. Google's documentation explicitly says it ignores sitemaps where every priority is the same. Use a meaningful range (homepage 1.0, categories 0.8, articles 0.6, archive 0.3 — or just leave priority out).

A <sitemapindex> is a sitemap-of-sitemaps. You need it when a single sitemap would exceed 50 000 URLs or 50 MB uncompressed. The index lists child sitemaps by URL; each child is a regular <urlset>. Google supports up to 50 000 child sitemaps per index, and indexes can be nested.

Per the spec, W3C Datetime — either a date (2026-06-04) or a full ISO 8601 timestamp with offset (2026-06-04T12:00:00+00:00). Anything else is flagged as a warning. Date.parse is permissive enough that most common formats validate, but stick to the spec to be safe across all search engines.