如果没有提供字符编码，HTML5是否为HTML文档指定了默认字符编码？ [英] Does HTML5 specify a default character encoding for HTML documents if no character encoding is supplied?

问题描述

通过HTTP检索的示例HTML文档缺少：

• HTTP Content-Type header


• HTML < meta charset =< character encoding> />


• a HTML < meta http-equiv ='Content-Type'content ='Type = text / html; charset =< character encoding>'>

示例UTF-8，假设为字符编码？

解决方案

字符集是使用以下规则确定的：

1. 用户覆盖。


2. Content-Type字段。


3. 字节顺序在HTML文档中的任何其他数据之前标记。


4. 属性。


5. 将http-equiv属性设置为Content-Type并为charset设置值的META声明。


6. 未指定的启发式分析。

...然后...

1. 根据Unicode技术标准＃22中定义的字符集别名匹配规则规范化给定的字符编码字符串。


2. 覆盖一些有问题的编码，编码好像是不同的编码。最常见的覆盖是将US-ASCII和ISO-8859-1视为Windows-1252，但此表中列出了其他一些编码覆盖。如规范所述，根据上表对某些编码作为其他编码进行处理的要求是对W3C字符模型规范的故意违反。

< blockquote>

但最重要的是：

strong>在每个 HTML文档上指定字符编码，或会发生错误。你可以用硬的方式（HTTP Content-Type头），简单的方法（< meta http-equiv> 声明） $ c>< meta charset> 属性），但请这样做。网络感谢您。

资料来源：

• http：// blog。 whatwg.org/the-road-to-html-5-character-encoding


• http://www.whatwg.org/specs/web-apps/current-work/multipage/parsing .html＃determining-the-character-encoding

An example HTML document retrieved over HTTP lacks:

• a HTTP Content-Type header
• a HTML <meta charset="<character encoding>" />
• a HTML <meta http-equiv='Content-Type' content='Type=text/html; charset=<character encoding>'>

With regards to HTML5, is a default, for example UTF-8, assumed as the character encoding? Or is it entirely up the application reading the HTML document to choose a default?

解决方案

The charset is determined using these rules:

1. User override.
2. An HTTP "charset" parameter in a "Content-Type" field.
3. A Byte Order Mark before any other data in the HTML document itself.
4. A META declaration with a "charset" attribute.
5. A META declaration with an "http-equiv" attribute set to "Content-Type" and a value set for "charset".
6. Unspecified heuristic analysis.

...and then...

1. Normalize the given character encoding string according to the Charset Alias Matching rules defined in Unicode Technical Standard #22.
2. Override some problematic encodings, i.e. intentionally treat some encodings as if they were different encodings. The most common override is treating US-ASCII and ISO-8859-1 as Windows-1252, but there are several other encoding overrides listed in this table. As the specification notes, "The requirement to treat certain encodings as other encodings according to the table above is a willful violation of the W3C Character Model specification."

But the most important thing is:

You should always specify a character encoding on every HTML document, or bad things will happen. You can do it the hard way (HTTP Content-Type header), the easy way (<meta http-equiv> declaration), or the new way (<meta charset> attribute), but please do it. The web thanks you.

Sources:

• http://blog.whatwg.org/the-road-to-html-5-character-encoding
• http://www.whatwg.org/specs/web-apps/current-work/multipage/parsing.html#determining-the-character-encoding

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