When writing HTML code and building web pages, a HTML validator is used to check and make sure the HTML code is correct, valid, and follows W3C standards set for HTML scripting. The HTML validator can check all the HTML markup and point any invalid code or any code that should be updated to better meet the W3C standards. Some HTML validators can also check XHTML, MathML, and SMIL scripting for validity.

Many free HTML validators are available. Some are web-based, meaning the HTML file can be loaded into the online validator and checked without having to install anything on the computer. Other validators work by installing the validator plug-in or extension in the web browser, or installing the validator software on the computer.

The W3C Markup Validation Service is one of the best HTML validators available, as it remains up-to-date with all new and updated HTML standards. The W3C validator checks HTML code by providing the web page URL, uploading the HTML file, or copying and pasting the HTML code into the validator.

An extension is available for Mozilla Firefox to allow a user to check HTML scripting right in the Firefox browser. The extension can be obtained from the Mozilla Addons site.

HTML, SEO Terms, W3C, Web design terms

  • How to test and check a web page for errors.
  • HTML and web design help and support.