Question 1

Which standards body maintains XML?

Accepted Answer

XML was developed by a working group within the World Wide Web Consortium (W3C) and became a W3C Recommendation in February 1998. It was designed as a simplified subset of SGML (ISO 8879) so the same documents could travel over the Web and be processed by off-the-shelf parsers. The XML 1.0 specification is now in its Fifth Edition (2008), and XML remains the foundation for SVG, XHTML, Atom, SOAP, Office Open XML, and countless enterprise data formats.

Question 2

How are XML attributes represented in the JSON output?

Accepted Answer

Attributes are preserved with an `@_` prefix, so `<user id="42">` becomes `{ "@_id": "42" }` in the JSON. Text content of a mixed element is stored under `#text`. When converting back from JSON to XML, any key starting with `@_` is restored as an attribute on the parent element, and `#text` becomes the element's text content. This convention is the default of fast-xml-parser.

Question 3

Why do repeated elements become arrays?

Accepted Answer

JSON has no native concept of "multiple children with the same name" — each property can hold only one value. When the parser sees `ab`, it collects the repeated `` elements into a JSON array so no data is lost. On the way back out, any array value under a key is serialized as that many repeated XML elements.

Question 4

Is the conversion lossless?

Accepted Answer

For most documents, yes — elements, attributes, text content, and nesting all roundtrip correctly. Things that can't be perfectly preserved: XML comments, CDATA sections, processing instructions, DOCTYPE declarations, and the exact order of attributes (JSON object key order is not spec-guaranteed). If your document depends on those, convert only one way and keep the original.

XML ↔ JSON Converter

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