XML Validator & Well-Formedness Checker
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An XML document doesn't need to match a schema to be usable, but it does need to be well-formed, with every tag properly opened, closed, and nested. This XML validator checks your document against those core well-formedness rules and reports exactly where it breaks down, whether that's an unclosed tag, mismatched nesting, or an invalid character. It's built for developers debugging feed parsers, integrators troubleshooting SOAP responses, and anyone maintaining hand-edited XML config files. Clear error messages point you directly to the problem instead of leaving you to scan the whole document manually. Validation runs entirely in your browser, so your XML is never uploaded to a server, and there's no signup required. Paste your XML below to check it instantly.
Features
- Checks XML for well-formedness per core XML rules
- Detects unclosed, mismatched, or improperly nested tags
- Flags invalid characters and malformed attributes
- Reports the exact location of each syntax issue
- Handles namespaces, CDATA, and processing instructions
- Works with both compact and beautified XML
- Instant feedback as you paste or edit
- Fully client-side validation with no data upload
Why use this xml validator?
- Finds structural XML errors in milliseconds
- Keeps sensitive documents private with local-only processing
- Pinpoints the exact tag causing the failure
- No setup needed - just paste and validate
- Free with unlimited validations
Frequently asked questions
What does it mean for XML to be well-formed?
Well-formed XML follows basic syntax rules: every tag is properly closed, elements are correctly nested, and there's exactly one root element.
Does this validator check against an XML Schema (XSD)?
No, this tool checks core well-formedness rules; validating against a specific XSD schema requires a schema-aware validator.
What's the most common XML error this tool catches?
Unclosed or mismatched tags are the most frequent issue, often from manual editing where a closing tag is forgotten or misnamed.
Is my XML uploaded to a server for validation?
No, validation runs entirely client-side in your browser, so your document is never sent anywhere.
Can it validate XML with namespaces?
Yes, namespace declarations and prefixed elements are parsed correctly as part of the well-formedness check.
Why would valid-looking XML still fail validation?
Invisible characters, mismatched case in tag names (XML is case-sensitive), or an unescaped ampersand in text content are common hidden causes.
Can I format the XML after validating it?
Yes, use the companion XML Formatter to beautify your document once it passes validation.