How do I validate a sitemap before converting?

Validate a sitemap against the sitemaps.org protocol: well-formed XML, ≤50,000 URLs, ≤50 MB uncompressed, <loc> values that are valid absolute URLs on the declared host, optional lastmod in W3C date format, priority in 0.0–1.0, and changefreq from the allowed set. xmlsitemapmaker.com's validator catches all of these in one pass — paste the URL or content, get back a list of errors and warnings. Common failures: malformed XML (unescaped &, missing closing tag), duplicate URLs, http/https hostname mismatches, invalid lastmod ('5/12/2024' isn't valid — must be 2024-05-12), priority values outside 0.0–1.0, and URLs on a different domain than the sitemap. Fix issues before converting; the converter trusts the input.