I can't disagree with making sure you're using them when they matter and avoiding them when they don't.
There was no real 'war', XHTML 5 is still a thing. Browsers are HTML engines because people who write HTML don't want to be forced into well-formed markup. They want the browser to guess what they meant and run with it.
There's also the whole "we need to be compatible with almost every HTML file dating back to the early 90s" conundrum that makes clean breaks in behavior, like XHTML, hard to pull off without pissing people off.
It should be clear which one is writing based on the DOCTYPE element. IIRC XHTML still requires a DTD to ensure its schema can be validated, while HTML 5 did away with it altogether and now just uses <!DOCTYPE html>
There was definitely a debate over how web browsers should interpret web pages - as XHTML or "quirks mode". HTML5 (with infinite backwards compatibility) was the outcome. Every major web browser implements HTML5 - complete with its super quirky and complex, but fully specified and consistent parsing rules.
> XHTML 5 is still a thing.
Is it though? On the web? I just tried, with this html:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html><body>
<div>
<div style="background-color: hotpink;" />
yo
</div>
</body></html>
Q: What do you expect the background-color of "yo" to be?
If this was an XHTML page, tags should be able to self-close. And in that case it should be black on white. But try it. Its not. The browser ignores the self-closing part of the tag, so "yo" is inside the inner div and it shows up in hot-pink. The outer div is then not closed correctly. (2 divs open, 1 div closes). If the page were processed as strict XHTML we'd also expect a warning or error, but the browser doesn't care. Neither firefox nor chrome emitted anything in the console about any of this.
As far as I can tell, the XHTML doctype has no effect here. The page is interpreted - as all webpages are - by the browser using HTML5's parsing rules. Not XHTML's.
There are contexts in which XHTML still exists. Like JSX. But the browser is not an XHTML renderer. Rail against HTML5 if you want, but people need to stop pretending that the browser supports self closing tags. They are not part of HTML5. Pretending they are causes bugs.
You need to serve it with the right mime time (application/xhtml+xml) or in case of local files use .xhtml extension. Then it's processed as XHTML and rendered as expected.
Also you need namespace declaration otherwise it will be rendered as unstyled xml.
I'm going to let this link to a simple XHTML document speak for itself. I've configured it to work on lighttpd via the `mime-types.conf` file, and even have a commented-out meta tag you can use to fake it in cases where you can't manipulate a server.
There was no real 'war', XHTML 5 is still a thing. Browsers are HTML engines because people who write HTML don't want to be forced into well-formed markup. They want the browser to guess what they meant and run with it.
There's also the whole "we need to be compatible with almost every HTML file dating back to the early 90s" conundrum that makes clean breaks in behavior, like XHTML, hard to pull off without pissing people off.
It should be clear which one is writing based on the DOCTYPE element. IIRC XHTML still requires a DTD to ensure its schema can be validated, while HTML 5 did away with it altogether and now just uses <!DOCTYPE html>