XML Formatter & Validator

Well-Formed Is Not Valid

A formatter can only verify that XML is well-formed: one root element, every tag closed, attributes quoted, entities escaped. It cannot check that the document obeys its schema — that an order element contains a date, or that an id attribute is unique. The other formatting decision that matters is whitespace significance: pretty-printing element content adds indentation characters inside mixed-content elements, which changes string values in data-centric XML. Format documents for reading; keep data files minified.

Well-Formed Is Not the Same as Valid

An XML parser checks that a document is well-formed: one root element, every tag closed and properly nested, attribute values quoted, and special characters such as & and < escaped. Those are the errors reported here with a line and column. Passing the check does not mean the data matches a schema; that requires validating against an XSD or DTD.

Formatting only adds whitespace between elements, which is harmless in data files but can matter in mixed content, where spaces between inline tags are part of the text. Minify before sending a payload and pretty-print only for reading or diffs.