Is the sitemap converter secure?

Yes. xmlsitemapmaker.com runs on Cloudflare Workers for the duration of one request and never stores the sitemap, URLs, file contents or any of the converted output. There's no database, no logs of URL content, and no analytics beyond aggregate page-view counts. The conversion happens server-side because some sitemaps (sitemap-index files, gzipped sitemaps, cross-origin URLs) can't be fetched from the browser due to CORS. For maximum privacy on sensitive URLs, use the Paste or Upload tabs instead of the URL tab — that way the sitemap content never leaves your machine before being sent to us as form data, processed in memory, and discarded.