XML validation checks that a document is well-formed — meaning it follows the core XML syntax rules. Well-formed XML has a single root element, all tags are properly closed and nested, attribute values are quoted, and special characters are escaped. This tool validates well-formedness using the browser's native XML parser.

Common XML Errors

Unclosed tags — every <tag> needs a matching </tag>
Case mismatch — <Item> and <item> are different tags
Unquoted or missing attribute values — must be id="value"
Unescaped special characters — & must be written as &

Frequently Asked Questions

Well-formed XML follows the basic XML syntax rules (proper nesting, quoted attributes, single root, escaped special chars). Valid XML additionally conforms to a specific schema (DTD or XSD). This tool checks well-formedness using the browser's DOMParser.

The most subtle issues are: using & instead of & in text, mismatched case in opening/closing tags, or extra content after the root element. Even one character out of place can break an XML document.

Schema validation requires a server-side processor. For XSD or DTD validation, tools like XMLSpy, oXygen, or the xmllint command-line tool support this. This tool validates well-formedness only.

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