Are line breaks allowed inside html tags?

Question

Is it allowed to have a line break inside a html tag? For example:

<h1
id="heading">

A first test in Chrome shows that this works, but is it specifically allowed by the spec and do all browsers (especially email clients) parse this correctly?

And what about in attributes?

<h1 
class="one
two">

In this case, will it be interpreted as a space?

(This last case is not answered in the "possible duplicate question")

Answer 1

yes that is acceptable! The browser will ignore line breaks and will teat them as spaces. So in you second example you will have an h1 element with two classes as attributes.

So

<h1 
class="one
two">

is the same as

< h1 class="one two">