Sitemap XML Validator 作者： Rajiv

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/