XML Schema Validator

This service lets you validate XML documents such as XHTML against the appropriate schemas. It performs a more accurate validation than the W3C validator. If you send XHTML documents as text/html, you should also test them in XHTML Proxy. See UITest.com for more validation tools.

This service does not perform generic XML Schema validation. While it can verify the well-formedness of any XML document, validation is only available with the built-in schemas. This validator does not download any DTD or schema files, but relies on its own ones.

You can validate XML documents by URL, by file upload or by direct input. Furthermore, you can validate fragments of XML documents. You can easily validate the page that is currently displayed in your browser with this bookmarklet.

Validate by URL

Address:
Schema:
Encoding:
HTML compatibility:
Output format:

Validate by file upload

File:
Schema:
Encoding:
HTML compatibility:
Output format:

Validate by direct input

Source:	<?xml version='1.0'?> <html xmlns='http://www.w3.org/1999/xhtml'> <head><title>…</title></head> <body> <p>…</p> </body> </html>
Schema:
HTML compatibility:
Output format:

Validate a fragment

Yes, you can validate portions of XML documents! Like a complete document, an XML fragment needs a namespace declaration to allow validation. Without a namespace declaration, only well-formedness constraints will be checked.

Fragment:	<p xmlns='http://www.w3.org/1999/xhtml'><em>…</em></p>
Schema:
HTML compatibility:
Output format:

Additional checks

Most document types are subject to constraints that cannot be expressed with XML Schema. This validator tries to check these as well, which makes its results much more applicable to real-world applications:

General
- Strict XML Schema validation
- Thorough check of language tags according to BCP 47
XHTML 1.0 and 1.1
- Check of element prohibitions
- Check of the HTML compatibility guidelines
  - XHTML elements with an empty content model must use <foo />, not <foo></foo>. (However, a missing space before the trailing / is not detected.)
  - XHTML elements with an non-empty content model must not use <foo />, but <foo></foo>.
  - Both xml:lang and lang attributes must be specified with the same value.
  - Avoid XML processing instructions.
  - Avoid comments inside style and script elements.
  - Avoid CDATA sections.
  - Avoid line breaks and multiple white space characters within attribute values.
Sitemaps 0.9
- Sitemaps files must be UTF-8 encoded.
BMEcat 2005
- The USER_DEFINED_EXTENSIONS element can contain arbitrary elements, but their names must start with UDX.

Requirements

This validator checks for namespace-well-formedness and namespace-validity, so e.g. <span id='foo:bar'> throws an error.

Known problems

Line breaks in end-tags might cause problems. While the validation is accurate, you might see improper source code lines in error messages.
There are some inconsistencies in the XHTML 1.0 specification. For instance, it is unclear whether the form element is allowed to carry a name attribute.
XML 1.1 is not supported. (XHTML 1.1 is supported, of course.)
XML Schema 1.1 is not supported either.
Support for xsd:any is limited. For example, xhtml:link elements in Sitemaps cannot be validated.

Implementation

This software is built around the System.Xml and System.Xml.Schema namespaces in .NET Framework 2.0. It is written in Visual Basic .NET.

The BMEcat 2005 schemas have been adapted during my work at businessMart AG.

Feedback

Don't hesitate to send suggestions and comments to Christoph Schneegans (christoph@schneegans.de).

Schema sources

The following schemas are used (with modifications where required):