How do I convert a gzipped sitemap (.xml.gz)?

Decompress the file first, then convert it. On macOS or Linux: gunzip sitemap.xml.gz produces sitemap.xml. On Windows, 7-Zip or WinRAR handle it. Most browsers also decompress .xml.gz when you visit the URL — open it directly and View Source to see the raw XML. Once decompressed, paste the content into the converter or upload the .xml file. xmlsitemapmaker.com doesn't currently auto-decompress .xml.gz client-side, so do this step yourself. If the file is gzipped because the sitemap is huge (>50 MB uncompressed), consider whether it should be split into a sitemap-index instead — large gzipped sitemaps are a sign the site is past the protocol's per-file ceiling.