How to Convert JSON to XML (and Back) Correctly

Why convert JSON to XML

You convert JSON to XML when a consumer only speaks XML: a SOAP web service, a partner API built on XML standards, or a legacy system whose parser predates JSON. The reverse — XML to JSON — is just as common when you receive RSS feeds, SOAP responses, or old config and want to work with it as modern JSON. The two conversions together let JSON and XML systems interoperate.

How keys become elements

The core mapping is straightforward: each JSON key becomes an XML element, and its value becomes the element's text or nested content. A nested JSON object produces nested elements, preserving the hierarchy. So {"user": {"name": "Ada"}} becomes a user element containing a name element with the text Ada.

{ "user": { "name": "Ada", "id": 1 } }

<user>
  <name>Ada</name>
  <id>1</id>
</user>

How arrays become repeated tags

XML has no array type, so a JSON array is rendered as repeated elements sharing one tag name — the idiomatic XML way to express a list. A JSON items array of three objects becomes three item elements in sequence. When converting back from XML, a good parser recognizes repeated sibling tags and collapses them into a JSON array so the round trip preserves the list.

{ "items": ["a", "b", "c"] }

<items>a</items>
<items>b</items>
<items>c</items>

The structural mismatches

• Attributes — XML elements can have attributes, which have no direct JSON equivalent; conversions either drop them or use a convention like an @ prefix.
• Namespaces — XML namespaces and prefixes do not exist in JSON and are typically flattened or lost.
• Order — XML preserves element order strictly; JSON object keys are unordered, so meaning carried by order can be lost.
• Mixed content — text interleaved with child elements is natural in XML but awkward to represent in JSON.

Valid XML element names

XML naming is stricter than JSON keys. An element name cannot contain spaces and cannot begin with a digit, while JSON keys can be almost anything. If your JSON has keys like "first name" or "123", a faithful conversion would produce invalid XML, so rename such keys in the JSON first. This is the most common reason a generated XML document fails to parse.

Converting reliably

Convert with a tool that parses and re-serializes rather than doing text substitution, so structure and escaping are handled correctly. The JSON to XML tool produces well-formed XML for SOAP and legacy consumers, and the XML to JSON tool turns feeds and responses into usable JSON. Validate the JSON side with a validator before converting, since malformed JSON cannot produce valid XML.