XML Formatter & Validator

Well-formed XML follows XML syntax rules: it has one document element, properly nested and closed tags, quoted attribute values, and valid character and entity syntax. Schema validation is a separate operation that checks the vocabulary and constraints chosen by a particular system.

This tool does not accept an XSD or any other schema, so Valid XML means only that the browser parser accepted the document as well formed. It cannot confirm that an invoice, feed, configuration file or API message meets the receiving application's rules.

An XML namespace associates a prefix, or a default namespace, with a URI so vocabularies can share a document without treating identical local names as the same expanded name. Formatting preserves those declarations and qualified names; it does not look up the namespace URI or judge whether the vocabulary is correct.

Mixed content places text and child elements in the same parent, as in <p>Hello <b>world</b>.</p>. Adding line breaks inside that element could change its text, so the formatter leaves an element containing non-whitespace text or CDATA serialized without structural line wrapping. CDATA preserves text that would otherwise need markup escaping; it does not make executable content safe in a later consumer.

Minify removes whitespace-only text nodes unless xml:space="preserve" applies. That can be useful between structural elements, but whitespace-sensitive document formats may assign meaning to those nodes. Keep an original copy and review the receiving format's rules before replacing it.

A DOCTYPE can define internal or external entities and can point a parser at another resource. Resolving untrusted external entities can expose local files, make unintended network requests or consume excessive resources. This tool rejects both DOCTYPE and ENTITY declarations before DOM parsing instead of trying to distinguish safe from unsafe declarations.

The restriction means XML that depends on a DTD, declared entity or external subset cannot be formatted here. The tool also performs no XInclude, schema loading or stylesheet transformation. Use a deliberately configured offline XML environment when those features are required.