Should I use <![CDATA[...]]> in HTML5?

Question

I'm pretty sure <![CDATA[...]]> sections can be used in XHTML5, but what about HTML5?

Answer 1

The CDATA structure isn't really for HTML at all, it's for XML.

People sometimes use them in XHTML inside script tags because it removes the need for them to escape <, > and & characters. It's unnecessary in HTML though, since script tags in HTML are already parsed like CDATA sections.

Edit: This is where we open that really mouldy old can of worms from 2002 over whether you're sending XHTML as text/html or as application/xhtml+xml like you’re “supposed” to :-)

Answer 2

From the same page @pst linked to:

Element-specific parsing for script and style tags, Guidance for XHTML-HTML compatibility: "The following code with escaping can ensure script and style elements will work in both XHTML and HTML, including older browsers."

Maximum backwards compatibility:

<script type="text/javascript"><!--//--><![CDATA[//><!--     ... //--><!]]></script> 

Simpler version, sort of incompatible with "much older browsers":

<script>//<![CDATA[    ... //]]></script> 

So, CDATA can be used in HTML5, and it's recommended in the official Guidance for XHTML-HTML compatibility.

This useful for polyglot HTML/XML/XHTML pages, which are served as strict application/xml XML during development, but served as text/html HTML5 in production mode for better cross-browser compatibility. Polyglot pages have their benefits; I've used this myself, as it's much easier to debug XML/XHTML5. Google Chrome, for example, will throw an error for invalid XML/XHTML5 (including for example character escaping), whereas the same page served as HTML5 will "just work" also known as "probably work".