Is html case sensitive?

Is HTML case sensitive?

HTML is Hypertext Markup Language, which is a standard markup language used to create web pages. When using HTML, we may encounter some problems with capitalization. So is HTML case sensitive?

The short answer is that HTML is not case-sensitive for tags, but it is case-sensitive for attributes and attribute values.

Regarding the case of HTML tags, in fact, after the release of HTML4.0 in 1997, the HTML language began to no longer be case-sensitive. Whether you use uppercase or lowercase letters, the tags will parse normally. For example, and are both completely legal forms of HTML tags.

Although HTML tags are not case-sensitive, in order to ensure the readability of the code when actually writing code, it is recommended to use lowercase characters to write HTML tags. This avoids confusion in the code and makes it easier for other readers to better understand and modify the code.

In contrast, attributes and attribute values ​​are case-sensitive. That is to say, if the attribute name or attribute value you write in HTML does not match the case, the browser will regard it as an error and cannot parse it correctly. For example, for the following code:

This is a test.

This is also a test.

The first paragraph will have the -demo-style applied to it, but the second paragraph will not. Because in CSS, style class selectors are case-sensitive. However, unlike writing attribute names and attribute values ​​in HTML, writing style class names and ID names in CSS is case-sensitive.

In addition to attributes and attribute values, HTML is also case-sensitive in URLs. If your URL is case-sensitive, the browser will display different content when accessing URLs with different capitalization.

To sum up, HTML is not case-sensitive in tags and attribute names, but it is case-sensitive in attributes, attribute values, and URLs. Therefore, when we write HTML code, we should try our best to ensure the consistency and readability of the code to avoid unnecessary errors.

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