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Being well-formed only means an XML document's syntax is valid — it doesn't mean the document has the right elements, in the right order, with the right types. This tool checks well-formedness always, and performs full XSD schema conformance validation if you paste a schema in.
How it works
The XML is parsed first; if it isn't well-formed, that's reported immediately. If you also supply an XSD schema, the document is validated against it using PHP's DOMDocument::schemaValidateSource() — real structural checking (required elements, order, types), not just syntax.
- Enter xML.
- Enter xSD schema (optional).
- Click Calculate to see your results.
Examples
Catching a missing required element
An XSD that requires a <book> element to contain a <title> will flag a document missing that element as invalid, even though the document is perfectly well-formed XML on its own.
Who should use it
- Validating an XML API payload or config file against its published schema.
- Testing a hand-written or generated XSD schema against sample documents.
Industry applications
- Enterprise data integration (XML is still heavily used in finance, healthcare, and government interchange formats)
- API and configuration validation
Advantages
- Performs genuine XSD structural validation, not just a well-formedness check, when a schema is supplied.
- Clearly reports which level of checking (well-formedness only, or full schema conformance) was actually performed.
Limitations
- Requires you to supply the XSD yourself — it doesn't infer or generate a schema from example XML.
Common mistakes to avoid
- Assuming "well-formed" and "schema-valid" mean the same thing — a document can be perfectly well-formed XML while still violating every rule in its schema.
- Pasting an XSD that itself has a syntax error, which prevents any validation from running at all.
Best practices
- Fix well-formedness errors first — schema validation can't even run until the document parses successfully.
- Keep your XSD schema and the XML you're validating in sync as the data format evolves.
Tips
- Use the plain XML Validator and Lint Tool if you only need a quick well-formedness check without maintaining an XSD.