Skip to main content

XML Validation

An XML document is valid if its contents match against a Document Type Declaration (DTD) or a XML Schema. This implies that the document must have a correct syntax and all the constraints defined in the schema are satisfied.

Well Formed XML Documents

An XML document is well-formed if its syntax is valid, i.e. if it satisfies the following rules:

  • XML documents must have a root element
  • XML elements must have a closing tag
  • XML tags are case sensitive
  • XML elements must be properly nested
  • XML attribute values must be quoted
<?xml version="1.0"  encoding="UTF-8"?>  
<body>Don't forget me this weekend!</body>

Remember that the XML parser is responsible for validating XML documents,

XML Documents with Errors

Errors in XML documents will stop your XML applications.

W3C specification states that a program should stop processing an XML document if it finds an error.

Valid vs Well Formed XML Document

A well formed XML document is different from a valid XML document.

A valid XML document must be well formed and must conform to a Document Type Definition (DTD) or to a XML Schema


Both DTD and XML Schema define the rules and legal elements and attributes for an XML document.

Learn more with our XML DTD Tutorial and XML Schema Tutorial