diff --git a/1.3-Implementation.md b/1.3-Implementation.md
index 0a3352f..b90da06 100644
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@@ -2,6 +2,7 @@
 
 - Read the [overview](https://github.com/ghacksuserjs/ghacks-user.js/wiki/1.1-Overview). It is important to understand how a `user.js` works with Firefox and what it can do.
 - Learn how to find and [back up](https://github.com/ghacksuserjs/ghacks-user.js/wiki/1.2-Backing-Up) your profile(s)
+- If you already have a `user.js`, consider using [Compare-UserJS](https://github.com/claustromaniac/Compare-UserJS), an excellent tool to compare user.js files and output the diffs in detailed breakdown - developed by our very own resident cat, [claustromaniac](https://github.com/claustromaniac) :cat2: 
 
 ### :small_orange_diamond: Very important, check these first...