blocks|key|2577162|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2577163|和XHTML有什么不同？|blockquote|2577164|2577165|2577166|有很多不同之处。|2577167|2577168|XML默认情况下有一个不同的命名空间，所以你必须使用xmlns="http://www.w3.org/1999/xhtml"命名空间，在|unordered-list-item|offset|length|style|CODE|2577169|+XML文档中显式使用xmlns="http://www.w3.org/1999/xhtml"是区分大小写的，而且你必须使用小写作为标记名和属性，甚至十六进制字符引用中的x+|2577170|XML也没有可选的开始和结束标签，所以你必须在XHTML文档中写出所有它们没有空标签，因此，您必须自己使用slash.|2577171|Non-void来结束每个空元素。|2577172|XML可以包含CDATA部分，即用<![CDATA[分隔的纯文本部分。另一方面，XML中没有CDATA、PCDATA元素或属性，因此您必须到处转义]]>符号(除了在CDATA+sections)|2577173|Quotes中，属性值在XML中不是可选的，并且没有属性最小化(仅名称attributes)|2577174|And+|2577175|解析器不能像HTML解析器那样容错。|2577176|2577177|然后有几个与XML无关的区别：|2577178|2577179|XHTML文档始终以标准模式呈现，从不以怪异模式呈现|2577180|XHTML不会查看头部的元命令来确定编码。事实上，在files.|2577181|Earlier文件中，W3C验证器会将<meta+http-equiv="content-type"+...标记为错误，但在XHTML1.0严格版和HTML4.01版严格版中，XHTML5文件中的HTML5不匹配会导致验证问题。XTHML1.0的定义缺少<img>和<form>上的name属性。但这是一个错误，已在XHTML1.1中修复。|2577182|2577183|您不能在HTML文档中真正使用XHTML，因为浏览器不会通过查看内容来区分这两种语法，而只能通过文件类型来区分。|2577184|换句话说，如果您有一个HTML文件，那么无论其中是否包含有效的XML，它的内容都是HTML。|2577185|关于语法规则，值得一提的是标记名的大小写。这意味着在HTML语言中，像console.log(document.body.tagName);这样的JavaScript命令将输出"BODY"，而在XHTML语言中，相同的命令将输出"body“。|2577186|2577187|不只是一种更严格的版本吗？|2577188|2577189|2577190|不是；XML与HTML有不同的规则，但它不一定更严格。如果说有什么不同的话，那就是XML的规则更少了！|2577191|在HTML中，许多功能是可选的。在XML中，您不必考虑这一点。XML更简单。|2577192|在HTML中，一些元素被定义为原始文本元素，即包含纯文本而不是标记的元素。|2577193|其他一些元素是可回避的原始文本元素，在这些元素中，诸如&#233;之类的引用将被解析，但诸如bold和之类的元素将被视为纯文本。如果您能够记住这些元素是什么，那么您就不必转义<符号(您也可以选择转义)。XML没有这样的内容类型，所以没有什么需要记住的，所有元素都有相同的内容类型。|2577194|2577195|XML以一种不同的方式解析注释。例如，HTML注释不能以注释掉<script>和<style>元素中的代码块。不要在HTML中尝试这样做。(由于兼容性问题，在XHTML中也不推荐这样做，但您可以这样做。)|2577197|2577198|如果它们的行为都一样，为什么会有不同的版本呢？|2577199|2577200|2577201|他们不会！当前版本的XHTML+(以前称为XHTML5)没有DTD，因此您必须使用数字引用，在本例中为&#233;和&#160;+(或者在DOCTYPE声明中自己定义这些实体)。X毕竟是eXtensible的意思)。|2577202|entityMap^0|0|0|0|0|0|0|Q|10|0|B|10|2D|1|0|0|0|H|9|21|3|0|0|0|0|0|0|0|0|0|J|Z|3J|5|3P|6|3X|4|0|0|0|0|Z|Z|0|0|0|0|0|0|0|0|R|6|1A|B|1M|G|32|1|0|0|S|5|17|1|0|A|G|T|8|12|7|0|0|0|0|0|1F|6|1M|6|0^^$0|@$1|2|3|-4|4|5|6|2B|7|@]|8|@]|9|$]]|$1|A|3|B|4|C|6|2C|7|@]|8|@]|9|$]]|$1|D|3|-4|4|5|6|2D|7|@]|8|@]|9|$]]|$1|E|3|-4|4|5|6|2E|7|@]|8|@]|9|$]]|$1|F|3|G|4|5|6|2F|7|@]|8|@]|9|$]]|$1|H|3|-4|4|5|6|2G|7|@]|8|@]|9|$]]|$1|I|3|J|4|K|6|2H|7|@$L|2I|M|2J|N|O]]|8|@]|9|$]]|$1|P|3|Q|4|K|6|2K|7|@$L|2L|M|2M|N|O]|$L|2N|M|2O|N|O]]|8|@]|9|$]]|$1|R|3|S|4|K|6|2P|7|@]|8|@]|9|$]]|$1|T|3|U|4|K|6|2Q|7|@]|8|@]|9|$]]|$1|V|3|W|4|K|6|2R|7|@$L|2S|M|2T|N|O]|$L|2U|M|2V|N|O]]|8|@]|9|$]]|$1|X|3|Y|4|K|6|2W|7|@]|8|@]|9|$]]|$1|Z|3|10|4|K|6|2X|7|@]|8|@]|9|$]]|$1|11|3|12|4|K|6|2Y|7|@]|8|@]|9|$]]|$1|13|3|-4|4|5|6|2Z|7|@]|8|@]|9|$]]|$1|14|3|15|4|5|6|30|7|@]|8|@]|9|$]]|$1|16|3|-4|4|5|6|31|7|@]|8|@]|9|$]]|$1|17|3|18|4|K|6|32|7|@]|8|@]|9|$]]|$1|19|3|1A|4|K|6|33|7|@]|8|@]|9|$]]|$1|1B|3|1C|4|K|6|34|7|@$L|35|M|36|N|O]|$L|37|M|38|N|O]|$L|39|M|3A|N|O]|$L|3B|M|3C|N|O]]|8|@]|9|$]]|$1|1D|3|-4|4|5|6|3D|7|@]|8|@]|9|$]]|$1|1E|3|1F|4|5|6|3E|7|@]|8|@]|9|$]]|$1|1G|3|1H|4|5|6|3F|7|@]|8|@]|9|$]]|$1|1I|3|1J|4|5|6|3G|7|@$L|3H|M|3I|N|O]]|8|@]|9|$]]|$1|1K|3|-4|4|5|6|3J|7|@]|8|@]|9|$]]|$1|1L|3|1M|4|C|6|3K|7|@]|8|@]|9|$]]|$1|1N|3|-4|4|5|6|3L|7|@]|8|@]|9|$]]|$1|1O|3|-4|4|5|6|3M|7|@]|8|@]|9|$]]|$1|1P|3|1Q|4|5|6|3N|7|@]|8|@]|9|$]]|$1|1R|3|1S|4|5|6|3O|7|@]|8|@]|9|$]]|$1|1T|3|1U|4|5|6|3P|7|@]|8|@]|9|$]]|$1|1V|3|1W|4|5|6|3Q|7|@$L|3R|M|3S|N|O]|$L|3T|M|3U|N|O]|$L|3V|M|3W|N|O]|$L|3X|M|3Y|N|O]]|8|@]|9|$]]|$1|1X|3|-4|4|5|6|3Z|7|@]|8|@]|9|$]]|$1|1Y|3|1Z|4|5|6|40|7|@$L|41|M|42|N|O]|$L|43|M|44|N|O]]|8|@]|9|$]]|$1|20|3|21|4|5|6|45|7|@$L|46|M|47|N|O]|$L|48|M|49|N|O]|$L|4A|M|4B|N|O]]|8|@]|9|$]]|$1|22|3|-4|4|5|6|4C|7|@]|8|@]|9|$]]|$1|23|3|24|4|C|6|4D|7|@]|8|@]|9|$]]|$1|25|3|-4|4|5|6|4E|7|@]|8|@]|9|$]]|$1|26|3|-4|4|5|6|4F|7|@]|8|@]|9|$]]|$1|27|3|28|4|5|6|4G|7|@$L|4H|M|4I|N|O]|$L|4J|M|4K|N|O]]|8|@]|9|$]]|$1|29|3|-4|4|5|6|4L|7|@]|8|@]|9|$]]]|2A|$]]

<blockquote>
 What is the difference between HTML and XHTML?
</blockquote>

There are many differences. The main one is that XHTML is HTML in an XML document, and XML has different syntax rules: 

<ul>
<li>XML has a different namespace by default, so you'll have to use the HTML namespace, <code>xmlns="http://www.w3.org/1999/xhtml"</code> explicitly in an XHTML document</li>
<li>XML is case sensitive and you'll have to use lowercase for tag names and attributes and even the <code>x</code> in hexadecimal character references</li>
<li>XML doesn't have optional start and end tags, so you'll have to write out all of them in full</li>
<li>Likewise, XML doesn't have void tags, so you'll have to close every void element yourself with a slash.</li>
<li>Non-void elements that have no content can be written as a single empty element tag in XML.</li>
<li>XML can contain CDATA sections, sections of plain text delimited with <code>&lt;![CDATA[</code> .. <code>]]&gt;</code>; HTML cannot</li>
<li>On the other hand, there are no CDATA or PCDATA elements or attributes in XML, so you'll have to escape your <code>&lt;</code> signs everywhere (except in CDATA sections)</li>
<li>Quotes around attribute values are not optional in XML, and there is no attribute minimization (name-only attributes)</li>
<li>And the XML parser is not as forgiving of errors as the HTML parser.</li>
</ul>

Then there are a couple of not XML-related differences:

<ul>
<li>XHTML documents are always rendered in standards mode, never in quirks mode</li>
<li>XHTML does not look at meta commands in the head to determine the encoding. In fact, the W3C validator flags <code>&lt;meta http-equiv="content-type" ...</code> as an error in XHTML5 files, but not in HTML5 files.</li>
<li>Earlier on, mismatches between the dtds for XHTML 1.0 strict and HTML 4.01 strict lead to validation issues. The definition for XTHML 1.0 was missing the <code>name</code> attribute on <code>&lt;img&gt;</code> and <code>&lt;form&gt;</code>. This was an error though, fixed in XHTML 1.1.</li>
</ul>

Note that XHTML documents should be served up with the correct file type, i.e. a .xhtml file extension or an application/xhtml+xml MIME type. You can't really have XHTML in an HTML document, because browsers don't differentiate between the two syntaxes by looking at the content, only by file type. 
In other words, if you have an HTML file, its contents are HTML, no matter if it has valid XML in it or not.

One point about the syntax rules worth mentioning is the casing of tag names. Although HTML documents are case-insensitive, the tag names are actually exposed as uppercase by the DOM. That means that under HTML, a JavaScript command like <code>console.log(document.body.tagName);</code> would output "BODY", whereas the same command under XHTML would output "body". 

<blockquote>
 Isn't XHTML merely a stricter version of HTML?
</blockquote>

No; XML has different rules than HTML, but it's not necessarily stricter. If anything, XML has fewer rules!

In HTML, many features are optional. You can choose to put quotes around attribute values or not; in XML you don't have that choice. And in HTML, you have to remember when you have the choice and when you don't: are quotes optional in <code>&lt;a href=http://my-website.com/?login=true&gt;</code>? In XML, you don't have to think about that. XML is easier.

In HTML, some elements are defined as raw text elements, that is, elements that contain plain text rather than markup. 
And some other elements are escapable raw text elements, in which references like <code>&amp;#233;</code> will be parsed, but things like <code>&lt;b&gt;bold&lt;/b&gt;</code> and <code>&lt;!-- comment --&gt;</code> will be treated as plain text. If you can remember which elements those are, you don't have to escape <code>&lt;</code> signs (you optionally can though). XML doesn't have that, so there's nothing to remember and all elements have the same content type.

XML has processor instructions, the most well known of which is the xml declaration in the prolog, <code>&lt;?xml version="1.0" encoding="windows-1252"?&gt;</code>. This tells the browser which version of XML is used (1.0 is the only version that works, by the way) and which character set.

And XML parses comments in a different way. For example, HTML comments can't start with <code>&lt;!--&gt;</code> (with a <code>&gt;</code> as the first character inside); XHTML comments can. 
Speaking of comments, with XHTML you can comment out blocks of code inside <code>&lt;script&gt;</code> and <code>&lt;style&gt;</code> elements using <code>&lt;!-- comment --&gt;</code>. Don't try that in HTML. (It's not recommended in XHTML either, because of compatibility issues, but you can.)

<blockquote>
 Why are there different versions of XHTML if they all act the same?
</blockquote>

They don't! For instance, in XHTML 1.1 you can refer to character entities like <code>&amp;eacute;</code> and <code>&amp;nbsp;</code>, because those entities are defined in the DTD. The current version of XHTML (formerly known as XHTML5) does not have a DTD, so you will have to use numerical references, in this case <code>&amp;#233;</code> and <code>&amp;#160;</code> (or, define those entities yourself in the DOCTYPE declaration. The X means eXtensible after all).

Note: this is supposed to be the canonical post for this question. A number of answers exist already, but descriptions of the various differences are scattered all over the place, and more often than not, they also offer opinions to "which one should I use", which I will refrain from in here. 
If you have more questions to ask, or you know of more differences, feel free to edit.

What is the difference between XHTML and HTML? Isn't XHTML merely a more strict version of HTML? And why are there different versions of XHTML if they all act the same?

What is the difference between HTML and XHTML?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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注意:这应该是这个问题的标准帖子。许多答案已经存在，但对各种差异的描述比比皆是，而且往往还提供了“我应该使用哪一个”的意见，我将在这里避免使用。如果你有更多的问题要问，或者你知道更多的不同之处，请随时编辑。XHTML和HTML之间的区别是什么？XHTML不只是HTML的一个更严格的版本吗？如果XHTML的行为都一样，为...

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