Do custom elements require a close tag?

Question

Elements I've defined (that don't require contents) seem to work just fine without a closing tag. I'm wondering if it's just a quirk of the browser though.

What's the verdict? Is it theoretically possible? What if the parser sees the element before its definition?

Answer 1

Yes. Custom elements require a closing tag. Only certain tags in HTML are allowed to be self-closing due to the parser.

The following is a complete list of the void elements in HTML:

area, base, br, col, command, embed, hr, img, input, keygen, link, meta, param, source, track, wbr

and :

A non-void element must have an end tag, unless the subsection for that element in the HTML elements section of this reference indicates that its end tag can be omitted.

http://www.w3.org/TR/html-markup/syntax.html#syntax-elements