Security & SEO

    How to use the free sitemap diff tool

    Compare two sitemap snapshots to see added, removed, and modified URLs — great for post-migration audits.

    Part of Sitemap monitoring — the full answer, the facts and the alternatives in one place.

    Updated 2026-07-10
    2 min read
    sitemap
    diff
    migration

    Quick answer#

    Paste two sitemap URLs (before and after) into /tools/sitemap-diff. You'll see added, removed, and lastmod-changed URLs side-by-side. Perfect for validating a site migration or CMS switch.

    What it does#

  1. Parses XML and sitemap indexes recursively
  2. Highlights added, removed, and modified URLs
  3. Flags URLs whose lastmod shifted
  4. Exports the diff as CSV
  5. Warns when a sitemap shrinks by >20% (a common migration red flag)

    6. Where to find it in Lemwatch#

    /tools/sitemap-diff — public, no signup. Paired with the in-app Sitemap Monitoring for continuous tracking.

    How to use it#

  6. Enter the "before" sitemap URL (e.g. archive.org copy or old CDN).
  7. Enter the "after" sitemap URL.
  8. Click Compare.
  9. Review added/removed URLs and download the CSV.
  10. Enable continuous monitoring inside Lemwatch to be alerted on future diffs.

    11. FAQ#

    Can I compare two files instead of two URLs?#

    Not in the free tool. Upload both to public URLs first, or use in-app sitemap monitoring.

    What if the sitemap is huge?#

    The tool handles up to 500,000 URLs. Beyond that, split the sitemap index or use the paid API.

    Related#

  11. Free broken link checker
  12. Free security header checker
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