HTML vs. XHTML: Key Differences and Best Practices
Understand the distinctions between HTML and XHTML, the stricter, XML-compliant version of HTML. This tutorial compares their DOCTYPE declarations, element case sensitivity, closing tags, attribute requirements, and more, helping you choose the right markup language for your projects.
HTML vs. XHTML
XHTML (Extensible HyperText Markup Language) is a stricter, XML-compliant version of HTML. While largely superseded by HTML5, understanding the differences is valuable.
What is XHTML?
XHTML is essentially HTML rewritten as an XML application. XML (Extensible Markup Language) is a markup language that enforces stricter rules for document structure and syntax compared to HTML.
Why XHTML?
XHTML's stricter syntax improves consistency and allows for better integration with other XML-based technologies. HTML is more forgiving of errors, while XHTML demands that all documents are "well-formed" (correctly structured).
For a more in-depth study of XML, refer to our XML Tutorial.
Key Differences Between HTML and XHTML
Here's a summary of the key differences:
| Feature | HTML | XHTML |
|---|---|---|
| DOCTYPE Declaration | Optional | Mandatory |
| `xmlns` Attribute in `html` | Optional | Mandatory |
| Element Case | Case-insensitive (<p> and <P> are equivalent) |
Must be lowercase (<p> only) |
| Element Nesting | Relatively flexible | Must be properly nested |
| Element Closing | Optional for some elements (e.g., <br>) |
All elements must be closed |
| Attribute Case | Case-insensitive | Must be lowercase |
| Attribute Quotes | Optional for some attributes | Always required |
| Attribute Minimization | Allowed (e.g., <input type="text" checked>) |
Forbidden |
(Illustrative examples demonstrating each of these points would be added here, using the `Correct` and `Wrong` format described in the original text.)
XHTML's stricter rules lead to better validation and interoperability but increased complexity.
XHTML Validation
You can validate your XHTML documents using the W3C validator to ensure they meet the required standards for well-formed XML.
(Link or form to W3C validator would be placed here)