What the comparison shows
Enter two sitemaps, or two domains. We read both in full (index files included, each file and each URL once) and compare the sets of page URLs:
- Added: in B, not in A.
- Removed: in A, not in B.
- In both, with a separate list of URLs whose lastmod changed.
- Format changes: added and removed URLs that differ only by https, www or a trailing slash.
Added and removed URLs are also grouped by their first folder, so you can see at a glance which section changed.
When to use it
- Before and after a migration or redesign. Compare the old site’s sitemap with the new one on staging. Every removed URL needs a 301 redirect to its closest new page, or a deliberate 404/410.
- After a deploy. A build that silently drops a section from the sitemap shows up as a block of removed URLs from one folder.
- Checking lastmod. If every URL’s lastmod changed between two runs a day apart, your sitemap writes the build date rather than real edit dates, and Google will learn to ignore it.
- Against a competitor. Every URL will differ, since the domains differ, but the section breakdown shows which folders they publish that you don’t.
Removed URLs aren’t automatically a problem. Pages you deleted on purpose, merged or noindexed should leave the sitemap. The ones to worry about are pages that still exist and still get traffic: check a few in Search Console before you accept the change.
Each side is capped at 50,000 unique URLs and 20 files. Lists show up to 500 URLs on the page and 5,000 per side in the CSV. For one sitemap on its own, use the URL extractor.