Paste your XML to check whether it's well-formed, catching unclosed tags, mismatched tags, and multiple root elements.
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Well-formed XML follows XML's basic syntax rules: every opening tag has a matching closing tag (or is self-closed), tags are properly nested without overlapping, and the document has exactly one root element containing everything else. This tool checks exactly those rules using its own hand-written parser.
'Well-formed' and 'valid' are different concepts in XML. Well-formed means the syntax is structurally correct, which is what this tool checks. 'Valid' additionally means the document conforms to a specific schema (like an XSD or DTD) defining which elements and attributes are allowed, this tool doesn't check schema validity.
Validating <root><item>value</item></root> returns 'Valid' with the message 'This XML is well-formed.' Validating <root><item>value</root> instead, where the </item> closing tag is missing, returns 'Invalid' with the message 'Mismatched closing tag: expected </item> but found </root>.', pinpointing exactly which tag pair doesn't line up.
Expecting a 'Valid' result to mean the document matches a particular schema, well-formedness only confirms correct tag structure, a well-formed document can still be 'invalid' against a specific XSD or DTD.
Assuming self-closing tags need an explicit closing tag, <br/> or <item/> are already complete on their own, adding </item> afterward would actually create a mismatched-tag error.
Not noticing that unescaped special characters (like a bare & or < inside text content) can break well-formedness, these need to be written as & and < when they're meant as literal text rather than markup.
The error message describes the specific tag or structural problem found (like which closing tag was unexpected), though it doesn't report a line number since the check is based on tag structure rather than raw text position.
No, all validation happens entirely in your browser, your data is never transmitted anywhere.
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