Sitemap XML Validator

Sitemap XML Validator gives developers, SEO teams, and QA engineers a fast, no-setup way to audit any XML sitemap directly from the Firefox toolbar.

HOW IT WORKS

Browse to a sitemap XML URL and click the toolbar icon — the add-on detects the page automatically and shows a one-click Validate button for the current tab URL. Alternatively, paste any sitemap URL into the input field to audit it without navigating there first.

XML STRUCTURE VALIDATION

The add-on parses the sitemap against the Sitemaps.org protocol and reports:

• Invalid root element (must be <urlset> or <sitemapindex>)
• Missing or incorrect xmlns namespace declaration
• Empty <loc> entries
• Malformed URL formats inside <loc>
• Incorrect <lastmod> date format (must follow W3C datetime)
• Invalid <changefreq> values (must be one of the 7 accepted values)
• Out-of-range <priority> numbers (must be 0.0 to 1.0) Each issue is tagged with its entry number for fast debugging.

URL REACHABILITY CHECKS

Every <loc> URL is fetched concurrently (8 at a time) and classified:

• Working (2xx) - URL is reachable and returns a success response
• Redirect (3xx) - URL redirects to another location
• Not Found (404) - URL does not exist
• Client Error (4xx) - Other client-side HTTP error
• Server Error (5xx) - Server returned an error response
• Timeout -

🙌 Acknowledgement

Special thanks to Rajat Singh for the idea and inspiration. LinkedIn: https://www.linkedin.com/in/rajat-singh-20260518a/