why <br /> and not <br/>?

Question

This is one of those things that you read once, say "aha!" and then forget. Exactly my case.

Why is the line-break tag in xhtml preferentially written with a space <br /> and not in the also ok format <br/> ? I remember the reason was interesting, and as you can imagine it's not easy to find with google.

For sure it's not an issue of xml well-formedness. From W3C

[44]    EmptyElemTag       ::=      '<' Name (S Attribute)* S? '/>' 

   Empty-element tags may be used for any element which has no content, whether
   or not it is declared using the keyword EMPTY. For interoperability, the 
   empty-element tag should be used, and should only be used, for elements which 
   are declared EMPTY.

Examples of empty elements:

<IMG align="left"  src="http://www.w3.org/Icons/WWW/w3c_home" /> 
<br></br> 
<br/>

So the space at the end is optional.

Answer 1

If I recall correctly it's simply because some older browsers had problems with a self-closing tag without a space before the slash. I doubt it's an issue nowadays, but a lot of developers (myself included) got into the habit of including the space.

Edit: Ah, here we are:

http://www.w3.org/TR/xhtml1/#guidelines

Include a space before the trailing / and > of empty elements, e.g. <br />, <hr /> and <img src="karen.jpg" alt="Karen" />. Also, use the minimized tag syntax for empty elements, e.g. <br />, as the alternative syntax <br></br> allowed by XML gives uncertain results in many existing user agents.

Answer 2

w3c specifies this as the grammar:

EmptyElemTag       ::=      '<' Name (S Attribute)* S? '/>'

That means open bracket, a name, a number of (space and attribute) tokens, an optional space, a slash, and an end tag. According to this, both are correct.

Answer 3

Some older browsers didn't parse the element correctly without the space, so most web developers use <br />. I don't remember which browsers offhand, but I believe they're just about extinct.

EDIT: The browser was Netscape 4.

Answer 4

There is no right way in XHTML. They are formally identical in XML. Whitespace is not significant in that location.

Answer 5

For XHTML: both of them. For HTML4 and earlier: neither.

Answer 6

<br /> is valid (old) HTML, while <br/> is not. If you are serving your XHTML as XML, it doesn't matter. If you are serving it as text/html, then it needs to be valid HTML in addition to being valid XHTML. (Why serve XHTML as HTML? Because IE doesn't understand XHTML as XML, and because no major browser will start rendering XHTML mid-way through downloading the text, but they will do that to HTML. My blog appears to load slowly not because the site is slow, but because the browser won't start rendering the page until everything has been fetched. I hate browsers.)

Answer 7

A little background to add to Matt Hamilton's answer.

A least one problem browser was Netscape 4. A quick check shows that in that browser, <br/> (i.e. no space) doesn't cause a line break. In fact, it doesn't appear to do anything. <br /> (i.e. with space) does perform a line break.

When creating polyglot documents that can behave as XHTML or HTML (Note: "behave as" - not "valid") it's necessary to use either <br /> or <br></br>. However, when parsed as HTML, </br> is treated as if it was <br>, so <br></br> produces two line breaks.

Answer 8

Both <br/> and <br /> are correct. The reason that <br /> came about in the first place was to support older browsers that didn't understand the new <br/> syntax. It's really kind of a hack where the / is interpreted as an attribute with no value and ignored.

Answer 9

Both are correct, and both will be accepted by web browsers. You may as well save yourself the extra character, and use <br/>

Answer 10

Both are correct. But I would use <br /> just to keep my code consistent... because I would never write

<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"/>

instead of

<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />

just to save a byte... and the second version is imho better readable. But that's just a matter of taste. Do it as you like, but do it consistent :-)

Answer 11

Either will work just fine. Assuming you are asking for evangelical reasons, I prefer <br/>

Answer 12

Both are correct.

Answer 13

<br>. You aren't using XML anyway.