---
title: "How to use the free sitemap diff tool — Lemwatch Help"
description: "Compare two sitemap snapshots to see added, removed, and modified URLs — great for post-migration audits."
canonical: "https://lemwatch.com/help/using-the-free-sitemap-diff-tool"
source: "https://lemwatch.com"
---

# How to use the free sitemap diff tool

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

## 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

- Parses XML and sitemap indexes recursively

- Highlights added, removed, and modified URLs

- Flags URLs whose lastmod shifted

- Exports the diff as CSV

- Warns when a sitemap shrinks by >20% (a common migration red flag)

## 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

- Enter the "before" sitemap URL (e.g. archive.org copy or old CDN).

- Enter the "after" sitemap URL.

- Click Compare .

- Review added/removed URLs and download the CSV.

- Enable continuous monitoring inside Lemwatch to be alerted on future diffs.

## 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

- Free broken link checker

- Free security header checker


## Related

- [Help centre](https://lemwatch.com/help)
- [How to use the free broken link checker](https://lemwatch.com/help/using-the-free-broken-link-checker)
- [How to use the free security header checker](https://lemwatch.com/help/using-the-free-security-header-checker)
- [How to use the free mixed content checker](https://lemwatch.com/help/using-the-free-mixed-content-checker)
- [Lemwatch pricing](https://lemwatch.com/pricing)
- [How to use the free SSL certificate checker](https://lemwatch.com/help/using-the-free-ssl-checker)