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Table of Contents
What is doctype and why does it matter?
There is only one correct way to write
Place on the first line of the HTML file
No extras needed
Home Web Front-end H5 Tutorial Declaring the correct HTML5 doctype for modern pages.

再接再厉 乘胜前进 不断把反恐维稳斗争引向深入..

Jul 03, 2025 am 02:35 AM
html5 doctype

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Doctype is a statement that tells the browser which HTML standard to use to parse the page. Modern web pages only need to write at the beginning of the HTML file. Its function is to ensure that the browser renders the page in standard mode rather than weird mode, and must be located on the first line, with no spaces or comments in front of it; there is only one correct way to write it, and it is not recommended to use old versions or other variants; other such as charset, viewport, etc. should be placed in the

section.

Declaring the correct HTML5 doctype for modern pages.

You only need to write at the beginning of the HTML page, which is the HTML5 declaration method that modern web pages should use. Simple and straightforward, no need to add anything else.

Declaring the correct HTML5 doctype for modern pages.

What is doctype and why does it matter?

The function of Doctype is to tell the browser: which HTML standard to use to parse this page. After HTML5 appeared, doctype was greatly simplified. In the past, the doctype of XHTML or HTML4 was very long and had to reference DTD files, but now it is enough to just say . When the browser sees this sentence, it is known that it should use standard mode to render the page, rather than be compatible with the old version of weird mode.

Declaring the correct HTML5 doctype for modern pages.

There is only one correct way to write

HTML5's doctype is case-sensitive, but we usually write in lowercase:

  • Correct writing method:
  • Error example:
    • (Although the browser can also recognize it, it is not recommended)
    • ..> (This is the writing method of the old version)

It must be placed in the front of the HTML file, and there must be no characters (including spaces and comments) in front of it, otherwise some browsers may enter weird mode.

Declaring the correct HTML5 doctype for modern pages.

Place on the first line of the HTML file

A common problem is that when using a template system or splicing HTML, sometimes blanks or comments are accidentally inserted before doctype. for example:

 <!-- This is a comment -->
<!DOCTYPE html>
<html>

This situation may cause the browser to misjudgment the document type. Therefore, it is recommended to check your build process or server-side output to ensure that <!DOCTYPE html> is the first content of the entire file.

No extras needed

Many people will wonder whether they need to add other content, such as charset, viewport or some meta tags. In fact, these doctype doctype, they should be placed in <head> part. The correct structure should be like this:

 <!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Page Title</title>
</head>
<body>
  ...
</body>
</html>

Basically that's it. It's very simple, but it's easy to make mistakes due to format problems.

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