About XML Files

XML (Extensible Markup Language) is a text-based format for structured data, ratified by W3C in 1998. Unlike HTML's fixed tags, XML lets developers define their own tags and nested structure, with optional schema validation. It underpins SVG, RSS, SOAP, DocBook, OpenDocument, and thousands of industry-specific standards.

XML files open in any text editor and every web browser (browsers show them as an expandable tree). For editing with validation, use VS Code with XML extensions, oXygen XML Editor, or Visual Studio. Most IDEs detect XML automatically and provide syntax highlighting.

Use KaijuConverter's XML-to-JSON converter, or command-line tools like xq (jq for XML). Programmatically, Python's xmltodict, JavaScript's xml2js, and .NET's JsonConvert.SerializeXmlNode all handle the conversion. Attributes typically become special keys (often prefixed with @) in the resulting JSON.

JSON for lightweight APIs and most modern web applications — smaller, faster to parse, native in every language. XML where schema validation, namespaces, mixed content, or industry standards (HL7, XBRL, DocBook) are required. XML also wins when documents need digital signatures (XML DSig).

XML is verbose by design — every tag has an opening and closing form, plus optional attributes. The same data in JSON is typically 30-50% smaller. This is intentional: XML trades bytes for human-readability and explicit structure.

XML is still essential in specific industries: healthcare (HL7 FHIR), finance (XBRL regulatory filings), publishing (DocBook, TEI), and anywhere schemas must validate. For new lightweight APIs, JSON has overwhelmingly replaced XML. Both are valid choices depending on the problem.