A browser can decide whether markup forms one properly nested XML document. It cannot infer the vocabulary, data types, required relationships, signature trust, or operational meaning expected by the system that receives it.
What well-formedness checks
XML 1.0 requires one document element, matching start and end names, proper nesting, quoted attribute values, unique attribute names, legal characters, and correct entity syntax. A fatal violation stops normal parsing. XMLClear exposes that browser parser boundary and the first line and column when the browser reports them. It does not guess a missing close tag or silently treat XML as forgiving HTML.
What validity adds
A DTD or schema can define which element names are allowed, their order and cardinality, attribute defaults, data types, and additional constraints. An application can impose still more rules: identifiers may need to exist elsewhere, totals may need to agree, a signature may need a trusted certificate, or a message may need a specific protocol version. A document can satisfy XML syntax and fail every one of those contracts. XMLClear therefore uses ‘well-formed’ and never labels the result schema-valid, trusted, secure, signed, or ready for production.
A practical review before use
Keep the original document beside the derived result and compare the part you intend to use. Confirm that element and attribute names, namespace prefixes and declarations, entity spellings, comments, processing instructions, CDATA boundaries, and mixed text read as expected. If the receiving system treats whitespace-only text as data, prefer Check or keep the original source rather than assuming a formatter can infer a missing content model. Finally run the result through the same schema, tests, signature checks, and application workflow that normally accepts this XML. XMLClear deliberately cannot prove those separate contracts.