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Mykhailo Seniutovych
Mykhailo Seniutovych

Reputation: 3691

Why do XHTML tags work in HTML5 documents and vice versa?

According to this document there are some XHTML tags, that are not supported in new HTML5 standard, for example big and strike. However when I declare my html document as HTML5 they still work for some reason, consider this example:

<!DOCTYPE html /> <!-- HTML5 decalration -->
<html>
    <head>
    </head>
    <body>
        <!-- These tags should not work, because the document is declared as HTML5, but they still work -->
        <big>Hello</big>
        <strike>123</strike>
    </body>
</html>

Same applies vice versa, there many other HTML5 tags that are not supported in XHTML standard, for example svg tag, however when I declare my document as XHTML they still work. Consider this example:

<!-- XHTML declaration -->
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">  
<html>
    <head>
    </head>
    <body>
        <!-- Should not work because SVG are not supported in XHTML standard -->
        <svg width="100" height="100">
            <circle cx="50" cy="50" r="40" stroke="green" stroke-width="4" fill="yellow" />
        </svg>
    </body>
</html>

The browser I used is the current version of Google Chrome. Can anyone explain why this is happening? What is the point of declaring the document as HTML5 or XHTML if the browsers will support both regardless of DOCTYPE specified?

Upvotes: 0

Views: 155

Answers (1)

leo848
leo848

Reputation: 667

In the first example:

These are so-called deprecated tags that you can still use in HTML5, but they're not recommended. They could be removed any time by browsers (although this is pretty unlucky).

The second example:

Most browsers like Google Chrome or Firefox don't render XHTML as XHTML. They actually render it in HTML5. The things that are different in XHTML are converted to HTML5 using a preprocessor. Because SVG isn't part of XHTML standard, it won't be converted but just stays as it is, and thus displayed like in HTML5.

Upvotes: 1

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