Website Validator

This program validates the html of an entire website at the press of a button. It's free. No ads, no tricks. I made it because I needed it at work and thought I might as well share it with others.

Website Validator (zip)
version 1.2.1
for Windows/Linux/Mac


  1. Download the zip file
  2. Unzip it to a folder
  3. Double click the jar file to run it (on Linux you might instead have to run the attached script)

Note: Requires Java

Validating a small website

You could use W3C Markup Validation Service url:

  1. Download and install Website Validator (WV)
  2. Start WV, using as Validator url

Validating a large website

You should install vnu, running it on your computer in order to avoid getting black listed at the W3C Markup Validation Service due to heavy traffic:

  1. Download the latest vnu<version>.jar (zip) from GitHub: Nu Html Checker (v.Nu)
  2. Extract the zip-file to a folder on your computer.
  3. Create a file called run-vnu.cmd (.sh for Linux, .command for Mac) in the same folder and put this command inside it:
    java -Xss1024k -cp vnu.jar nu.validator.servlet.Main 8888
  4. Double click/run run-vnu.cmd
  5. Point your browser to http://localhost:8888 to make sure it runs
  6. Download and install Website Validator (WV)
  7. Start WV, using http://localhost:8888 as Validator url


After validation a report is displayed and saved in your home folder in subfolder "Website Validator report" (in Windows: c:\users\<username>\Website Validator report).

Website Validator screenshot
Website Validator report screenshot


Version 1.2.1 - 21 March 2021
  • Reports are saved with unique file names and therefore no longer overwrite old reports.