Not every html tag has a closing tag. "<br />" parsing is supported in html5 as recognizing self closing xml tags is necessary due to people publishing xhtml wi

Not every html tag has a closing tag. "<br />" parsing is supported in html5 as recognizing self closing xml tags is necessary due to people publishing xhtml with an html mime type. But to be clear it's incorrect: <br>...</br> is incorrect as <br> is a self closing tag, so the closing tag itself is erroneous. In terms of validation: html5 has a specified parsing algorithm, you can validate html against it. That validation is not xml validation. Again, because html is not xml. There is a very clear specification about how html tags are parsed, trying to reason about html as if it is xml is just as (if not more) incorrect than trying to reason about C as if it were C++. e.g. void f(); Is a different type in C than it is in C++, but if you do this you can't turn around and complain that C and C++ see it as having a different type when the syntax has different meanings.