They are not self-closing elements. They are void elements.
Void elements must not have end-tags. In HTML5, <br>
and <br />
mean the same thing: they are both start tags! It just so happens that no end tag is required for these elements. There is no concept of a self-closing tag in HTML5.
So you might as well write these without the slash, although I personally find it more readable if the slash is present.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…