diff --git a/DEVTools.md b/DEVTools.md
index cee5475ef..314f275d0 100644
--- a/DEVTools.md
+++ b/DEVTools.md
@@ -462,6 +462,7 @@
 * [HTML Reference](https://htmlreference.io/) - *HTML Guide* 
 * [HTML Compressor](https://htmlcompressor.com/compressor/)
 * [HTML Notepad](https://html-notepad.com/) - *HTML Editor*
+* [Markup Validation Service](https://validator.w3.org/) - *Validate Your Markup Language Structure*
 * [typeset](https://typeset.lllllllllllllllll.com/) - *HTML Typography Pre-Processor*
 * [TryIt HTML](https://www.w3schools.com/html/tryit.asp?filename=tryhtml_intro), [CodeTester](http://codetester.org/), [HTML-Online](https://html-online.com/editor/), [html.cafe](https://html.cafe/) or [jsTester](https://www.cs.iupui.edu/~ajharris/webprog/jsTester.html) - *Online HTML Editors / Testers* 
 * [HTMLColorCodes](https://htmlcolorcodes.com/) - *HTML Color Codes*