This plugin hasn’t been tested with the latest 3 major releases of WordPress. It may no longer be maintained or supported and may have compatibility issues when used with more recent versions of WordPress.

42U HTML5 Upgrade


The 42U HTML5 Upgrade prepares your older site for HTML5 and allows you to start using HTML5 structure tags right now in your posts and pages (section, aside, article, etc), regardless of the browser viewing them.

The 42U HTML5 Upgrade plugin loads Modernizr, enables the HTML5 Schema in the TinyMCE Editor and adds HTML5 elements to the TinyMCE style list.

The custom Modernizr build includes all CSS3, HTML5 and Misc tests, as well as the html5shiv w/printshiv and Modernizr.load(). See the options we used here.

You can turn these functions off individually if you wish!


  1. Upload the 42UHTML5 directory (including all files within) to the /wp-content/plugins/ directory
  2. Activate the plugin through the ‘Plugins’ menu in WordPress


Who should use this plugin?

Anyone with an older site template that is not written to HTML5 standards.

Is it multisite compatible?

You betcha.

Will this break my current site?

Probably not. We deployed this on over 350 sites that we host and didn’t see a single problem.

Will this make old browsers suddenly work with new HTML5 features?

From the modernizr docs:

The library does allow you to use the new HTML5 sectioning elements in IE, but aside from that, it doesn’t modernize any other features. However! Modernizr still pairs extremely well with scripts that do provide support when native browser support is lacking. In general, these scripts are called polyfills.
polyfill (n): a JavaScript shim that replicates the standard API for older browsers

That means you can develop for the future, with the real API, and only load your compatibility polyfills on browsers that do not support that API or feature.

And good news for you, there is a polyfill for nearly every HTML5 feature that Modernizr detects. Yup. So in most cases, you can use a HTML5 or CSS3 feature and be able to replicate it in non-supporting browsers. Yes, not only can you use HTML5 today, but you can use it in the past, too!

See for an extensive list of available polyfills.


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Contributors & Developers

“42U HTML5 Upgrade” is open source software. The following people have contributed to this plugin.


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Interested in development?

Browse the code, check out the SVN repository, or subscribe to the development log by RSS.



  • Updated modernizr.js to 2.6.2.


  • Set TinyMCE visualblocks plugin display default to false.


  • Added TinyMCE visualblocks plugin. This makes HTML5 elements easier to work with in the visual editor.


  • Initial release.