HTML 5: Is it , , or ?

Question

I\'ve tried checking other answers, but I\'m still confused — especially after seeing W3schools HTML 5 reference.

I thought HTML 4.01 was supposed to \"allow\" singl

Answer 1

1. If you are outputting HTML on a regular website you can use
or
, both are valid anytime you are serving HTML5 as text/html.

2. If you are serving HTML5 as XHTML (i.e. content type application/xhtml+xml, with an XML declaration) then you must use a self closing tag like so:
.

   If you don't the some browsers may flat out refuse to render your page (Firefox in particular is very strict about rendering only valid xhtml+xml pages).

   As noted in 1.
is also valid for HTML5 that happens to be generated as XML but served as a regular text/html without an XML declaration (such as from an XSL Transform that generates web pages, or something similar).

To clear up confusion: Putting a space before the slash isn't required in HTML5 and doesn't make any difference to how the page is rendered (if anyone can cite an example I'll retract this, but I don't believe it's true - but IE certainly does a lot of other odd things with all forms of
tags).

The excellent validator at http://validator.w3.org is really helpful for checking what's valid (although I'm not sure you can rely on it to also check content-type).