📰 XML Formatter & Validator
Format, indent and minify XML - runs entirely in your browser
<?xml version="1.0"?>
<catalog>
<book id="bk101">
<author>Gambardella, Matthew
</author>
<title>XML Developer Guide
</title>
<price>44.95
</price>
</book>
<book id="bk102">
<author>Ralls, Kim
</author>
<title>Midnight Rain
</title>
<price>5.95
</price>
</book>
</catalog>How to Use the XML Formatter
Paste any XML document into the left panel. Click Format to pretty-print with indentation (choose 2 or 4 spaces), or Minify to collapse it to a single line for production use. XML is used for SOAP APIs, RSS feeds, Maven POM files, Android layouts, SVG files, and countless configuration formats. Formatted XML is much easier to read and debug than a single-line blob.
Common use cases: Format a SOAP response to find the data fields. Minify a large XML config for faster transmission. Compare XML structures by formatting both before using a diff tool. All processing is client-side - your XML data never leaves your browser.
What is the difference between well-formed and valid XML?
Well-formed XML meets the basic XML syntax rules: every opening tag has a matching closing tag, tags are properly nested (no overlapping), the document has exactly one root element, attribute values are quoted, and special characters are escaped. Valid XML goes further — it also conforms to a schema (DTD or XSD) that defines which elements and attributes are allowed and their structure. A well-formed XML file passes a basic XML parser. A valid XML file also passes schema validation. Most XML processing requires only well-formedness; schema validation is used for data exchange standards like SOAP, XBRL, or OpenDocument.
What are the most common XML syntax errors?
Unmatched tags: <item><name>Alice</item></name> — name closes before item. Overlapping tags: <b><i>text</b></i> — tags must properly nest. Missing quotes: attr=value instead of attr='value'. Unescaped special characters in content: & must be &, < must be <, > should be >, ' should be ', " should be " in attribute values. Multiple root elements: XML must have exactly one root. Missing XML declaration encoding: <?xml version='1.0' encoding='UTF-8'?> is recommended. Case sensitivity: <Item> and <item> are different elements in XML (unlike HTML).
What is the difference between XML namespaces and prefixes?
XML namespaces prevent element name conflicts when combining XML from different sources. A namespace is a URI: xmlns:xsd='http://www.w3.org/2001/XMLSchema'. The xsd: prefix is just a shorthand — the actual namespace is the URI. Two elements with different prefixes but the same URI are in the same namespace. The default namespace (xmlns='http://example.com') applies to all unprefixed elements in scope. Common namespaces: SOAP envelope (xmlns:soap), XML Schema (xmlns:xs), SVG (xmlns='http://www.w3.org/2000/svg'), XHTML. Namespace URIs do not need to be real URLs — they are just unique identifiers.
When should I use XML vs JSON for data exchange?
XML advantages: attributes (metadata separate from content), comments (JSON has none), mixed content (text and elements interleaved — common in documents), namespaces (combining vocabularies), XSLT transformation, XPath querying, and extensive tooling for enterprise integration (SOAP, XBRL, EDI). JSON advantages: more compact, natively parsed by JavaScript, simpler data model, human-readable for APIs. Modern preference: JSON for REST APIs and JavaScript applications. XML remains dominant in: enterprise B2B data exchange, document formats (DOCX, ODT, SVG), configuration in Java/enterprise ecosystems (Maven, Spring), and legacy system integration.
How do I query XML data to extract specific values?
XPath is the query language for XML: //book[@category='fiction']/title extracts all fiction book titles. In JavaScript: const result = document.evaluate('//title', xmlDoc, null, XPathResult.ANY_TYPE, null). In Python: from lxml import etree; tree.xpath('//book/title/text()'). In Java: XPathFactory.newInstance().newXPath().evaluate(). The XML to JSON converter on this site transforms XML to JSON, after which you can use JSONPath expressions instead of XPath if you prefer that query syntax.
How do I validate XML against an XSD schema?
XSD (XML Schema Definition) defines the allowed structure, data types, and constraints for an XML document. Validation tools: in a browser this is limited. For production validation: Java has built-in JAXP support; Python has lxml: from lxml import etree; schema = etree.XMLSchema(etree.parse('schema.xsd')); schema.validate(doc). The xmllint command-line tool validates against XSD: xmllint --schema schema.xsd data.xml. Online validators accept both the XML file and the XSD schema. This tool validates well-formedness only — not schema compliance.
What other format conversion tools are on this site?
The XML to JSON converter transforms XML to JSON format. The JSON Formatter handles the JSON output from XML conversion. The YAML Formatter covers another major configuration format. The Diff Checker compares two XML file versions. The HTML Validator is related but specifically for HTML5 — XML and HTML have different rules. All are in the Dev Tools section.
📊 Key Data Points
DOMParser
Browser-native XML parser — handles namespaces, CDATA, and processing instructions
parsererror
XML validity errors surfaced as parsererror elements with line/column information
Well-formed vs Valid
This validates well-formedness (structure). Schema validation (DTD/XSD) is a separate step
XML Formatter & Validator -- Complete USA Guide 2026
Minified XML from APIs or legacy systems is as unreadable as a single-line HTML file. Formatting adds indentation and line breaks to reveal the document structure.
This formatter uses the browser native DOMParser to validate and reformat XML. Runs entirely in your browser.
**Long-tail searches answered here:** format and indent XML online free, XML validator that shows line number of error, pretty print XML without installing software.
For data transformation, pair with XML to JSON.
🔬 How This Calculator Works
Passes your XML through the browser native DOMParser.parseFromString() with text/xml MIME type. If well-formed, returns a document object; if not, returns a parsererror document with the error location.
Formatting serializes the DOM back to a string with added 2-space indentation per level, preserving all attributes, namespace declarations, CDATA sections, and processing instructions.
✅ What You Can Calculate
Native XML validation
Uses the browser built-in XML parser — reports the exact line and column where well-formedness is violated.
Preserves namespaces and CDATA
Namespace prefixes, CDATA sections, processing instructions, and XML declarations are all preserved intact during formatting.
Minify for payload comparison
Toggle to minified output to see the actual byte size of your XML payload. Useful before adding XML compression middleware.
No external parser dependency
Relies on the browser built-in DOMParser — no external library, no npm package. Works on restricted corporate networks.
🎯 Real Scenarios & Use Cases
Debugging SOAP responses
SOAP API responses arrive as single-line XML strings. Paste here to see the envelope, header, and body structure clearly indented.
Validating Android and iOS resource files
Android strings.xml and iOS plist files are XML. Validate here before committing to catch malformed tags that cause cryptic build failures.
Reading Maven POM files
Maven pom.xml files are deeply nested XML. Format here to understand dependency trees and plugin configurations without an IDE.
Formatting SVG files
SVG is XML. Minified SVG exported from Figma or Illustrator is impossible to read. Format here before editing path data or adding animations.
💡 Pro Tips for Accurate Results
Well-formed vs valid. This tool checks XML well-formedness — every tag closed, attributes quoted, no illegal characters. It does not validate against a DTD or XML Schema (XSD).
Namespace errors are verbose. If your XML uses namespace prefixes not declared in the document, DOMParser reports confusing errors. Check that every prefix:element has a corresponding xmlns:prefix declaration.
SVG formatting. SVG files are valid XML. Format minified SVG exports here to make them human-editable. Then use SVG Optimizer to clean unnecessary attributes.
CDATA vs entities. CDATA sections and entity-encoded content are both preserved as-is during formatting.
🔗 Use These Together
🏁 Bottom Line
XML is verbose even when well-formatted. Minified XML is effectively unreadable. This formatter restores structure using the browser own parser.
For data transformation: format here to understand the structure, then convert with XML to JSON or compare changes with Diff Checker.