XML Formatter

How it works

XML Quick Reference

XML vs JSON at a Glance

Tips & Tricks

Code Examples

const { XMLParser, XMLBuilder } = require('fast-xml-parser');

const parser = new XMLParser({ ignoreAttributes: false, attributeNamePrefix: '@_' });
const builder = new XMLBuilder({ ignoreAttributes: false, attributeNamePrefix: '@_', format: true, indentBy: '  ' });

const xml = `Alice`;
const parsed = parser.parse(xml);
const formatted = builder.build(parsed);
console.log(formatted);

import xml.dom.minidom
import xml.etree.ElementTree as ET

# Pretty-print XML
raw = 'Alice'
dom = xml.dom.minidom.parseString(raw)
print(dom.toprettyxml(indent='  '))

# Parse XML into a tree
tree = ET.parse('config.xml')
root = tree.getroot()
for child in root:
    print(child.tag, child.attrib)

# Format XML with xmllint (install: brew install libxml2)
xmllint --format file.xml

# Validate XML against a schema
xmllint --schema schema.xsd file.xml

# Format and save
xmllint --format file.xml -o formatted.xml

# Convert XML to JSON with python
python3 -c "import sys,json,xml.etree.ElementTree as ET; \
  t=ET.parse(sys.argv[1]); print(json.dumps({t.getroot().tag:{}}))" file.xml

Frequently Asked Questions

What does XML stand for?

XML stands for Extensible Markup Language. It is a text-based format for storing and transporting structured data, defined by the W3C. Unlike HTML, XML has no predefined tags — you define your own tag names to describe your data. XML is used in configuration files, APIs (SOAP, RSS, Atom), office document formats (DOCX, XLSX), and data interchange between systems.

What is an XML formatter?

An XML formatter (also called an XML beautifier or XML pretty printer) takes compact or minified XML and adds indentation and line breaks so the structure is human-readable. It parses the XML into a tree, then serializes it back with consistent indentation. A formatter also validates the XML — if the input is not well-formed, it reports the exact line and column of the error.

Is my XML data sent to a server?

No. All formatting, validation, and conversion runs entirely in your browser using JavaScript. Your data never leaves your machine and no account or sign-up is required.

What is the difference between well-formed and valid XML?

Well-formed XML follows the basic XML syntax rules: every opening tag has a matching closing tag, attributes are quoted, tags are properly nested, and there is exactly one root element. Valid XML additionally conforms to a schema (DTD or XSD) that defines which elements and attributes are allowed. This formatter checks for well-formedness — schema validation requires a separate XSD validator.

What are the most common XML errors?

The most common XML errors are: unclosed tags (every opening tag needs a closing tag or self-closing form), mismatched tags, unquoted attribute values, special characters not escaped as entities (& < > ' "), and multiple root elements (XML requires exactly one root). The formatter reports the exact line and column of the first error.

How do I convert XML to JSON?

Use the Convert → JSON button. XML attributes are included in the JSON output prefixed with @_ (e.g. <user id="1"> becomes {"user": {"@_id": "1"}}). Note that XML's ordered elements and repeated sibling tags do not map cleanly to JSON objects — review the output carefully for elements with multiple children of the same tag name.

What is the difference between XML and HTML?

HTML is a specific application of markup designed for web pages with fixed tags (div, p, img, etc.) and a forgiving parser that handles unclosed tags and other errors. XML is a general-purpose format where you define your own tags, and the parser is strict — any syntax error stops processing. XHTML is HTML reformulated as strict XML. Modern web development uses HTML5 (not XML-based), while XML is used for data interchange, configuration, and document formats.

What are XML namespaces?

XML namespaces prevent tag name collisions when combining XML from different sources. A namespace is declared with the xmlns attribute: <root xmlns:app="https://example.com/app">. Tags in that namespace use the prefix: <app:user>. Namespaces are common in SOAP web services, SVG, and Office Open XML formats. The formatter preserves namespace declarations in the output.

How do I minify XML?

Click the Minify button to remove all whitespace between tags and produce the most compact valid XML. In Node.js, use fast-xml-parser's XMLBuilder with format: false. In Python, use xml.etree.ElementTree to parse and re-serialize without pretty-printing. Minified XML reduces file size for network transfer and storage.

What is CDATA in XML?

CDATA (Character Data) sections let you include text containing XML special characters without escaping them. A CDATA section looks like <![CDATA[ raw content here ]]>. Everything inside is treated as literal text, not markup. CDATA is useful for embedding HTML, code snippets, or SQL inside XML documents. The formatter preserves CDATA sections in the output.

What is the XML declaration?

The XML declaration is an optional first line: <?xml version="1.0" encoding="UTF-8"?>. It specifies the XML version (always 1.0 in practice) and the character encoding. If omitted, parsers assume UTF-8. The declaration must appear before the root element and before any other content. It is recommended for documents that may be processed by systems with different default encodings.

What is XPath and how is it used?

XPath is a query language for selecting nodes in an XML document. It uses path expressions like /root/users/user[@id='1']/name to navigate the tree. XPath is used in XSLT transformations, Selenium web testing, and XML processing in Python (xml.etree.ElementTree supports XPath subsets). XSLT uses XPath to define which XML nodes to transform and how to render them.

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