Do I need a schema to validate?

No, basic validation checks well-formedness only. Schema validation is additional. Use schemas when you need to enforce specific document structure.

Why do special characters cause errors?

XML reserves & " '. Use entities: < > & " '. Or wrap content in CDATA sections: chars]]>.

How do I handle namespaces?

Namespaces use prefixes (xmlns:prefix="uri"). Elements must use declared prefixes. Validation should consider namespace-aware parsing for complex documents.

XML Validator

Guide & TutorialOffline

Validate and format XML documents

Validate and format XML documents instantly with our free online XML validator. This tool helps developers and data engineers check XML syntax, verify well-formedness, and beautify XML for better readability. Simply paste your XML document and get instant validation with formatted output.

Input XML

0 characters, 1 lines

Validation Result

About XML Validation

XML (eXtensible Markup Language) is a markup language for encoding documents. This validator checks if your XML is well-formed according to XML specifications.

Common errors:

Unclosed tags or mismatched opening/closing tags
Missing or invalid XML declaration
Invalid characters in tag names
Improperly nested elements
Missing quotes around attribute values

About XML Validator

XML validation checks documents for well-formedness and optionally validates against DTD or XSD schemas. Well-formed XML has proper syntax; valid XML conforms to a defined structure. Validation catches errors that would cause parsing failures.

How It Works

The validator checks well-formedness: proper tag nesting, closed tags, quoted attributes, valid characters. Schema validation additionally checks: required elements, correct structure, data types, attribute constraints. Reports include line numbers and error descriptions.

Technical Details

Well-formed XML rules: single root element, properly nested tags, closed tags (or self-closing), quoted attribute values, case-sensitive tags, no invalid characters. Schema validation (XSD/DTD) adds structural rules, data types, and constraints.

Common Use Cases

Configuration Files

Validate XML config files (web.config, pom.xml).

Catch unclosed tags in Maven POM

Data Exchange

Validate XML data before processing.

SOAP/Web Services

Validate SOAP messages and WSDL.

Document Formats

Validate SVG, XHTML, RSS feeds.

Code Examples

Common XML Errors

xml

<!-- Not well-formed: unclosed tag -->
<root>
  <item>Content
</root>

<!-- Not well-formed: improper nesting -->
<root>
  <a><b></a></b>
</root>

<!-- Not well-formed: unquoted attribute -->
<element attr=value />

<!-- Not well-formed: unescaped special char -->
<data>5 < 10</data>

<!-- Well-formed XML -->
<root>
  <item>Content</item>
  <data><![CDATA[5 < 10]]></data>
</root>

XML has strict syntax rules. Tags must close, nest properly, attributes must be quoted, and special characters must be escaped.

Tips & Best Practices

Always close tags or use self-closing syntax
Quote all attribute values
Escape special characters or use CDATA
Use consistent casing for tag names
Validate against schema for structural correctness

Common Mistakes to Avoid

Forgetting to close tags
Improper nesting of elements
Unquoted attribute values
Unescaped special characters

When to Use This Tool

Validate XML for configuration files, data exchange, web services, and document formats. Essential before parsing or processing XML data.

Frequently Asked Questions

Well-formed means correct syntax (proper nesting, closed tags). Valid means conforming to a schema (DTD/XSD) that defines allowed elements, structure, and data types. All valid XML is well-formed, but not vice versa.

Related Tools

CSS Validator

Validate css syntax and structure. Real-time validation with detailed error messages. Essential for developers, QA testers, and data analysts.

Javascript Validator

Validate javascript syntax and structure. Real-time validation with detailed error messages. Essential for developers, QA testers, and data analysts.

TFN Validator

Validate tfn syntax and structure. Real-time validation with detailed error messages. Essential for developers, QA testers, and data analysts.

 <root> <item>Content </root>  <root> <a><b></a></b> </root>  <element attr=value />  <data>5 < 10</data>  <root> <item>Content</item> <data><![CDATA[5 < 10]]></data> </root>