XML Validator

Validate XML syntax and check for well-formedness. Identify parsing errors with detailed error messages and line numbers.

100% client-side No signup Free forever
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How to Use XML Validator

  1. Paste your XML content into the input textarea
  2. Click "Validate XML" to check for syntax errors
  3. Use "Format" to beautify your XML with proper indentation
  4. Use "Minify" to compress XML for production use
  5. View the tree structure for visual representation
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About XML Validator

XML documents must be well-formed to be parsed by applications. A single missing bracket or improperly nested tag breaks the entire document. Our validator checks your XML and provides precise error messages to help you fix problems quickly.

What Gets Validated

The validator checks multiple aspects:

  • Well-formedness: Proper tag nesting, closed elements, valid characters
  • Syntax: Correct attribute quoting, entity encoding
  • Structure: Matching start and end tags, single root element
  • Encoding: Valid UTF-8 or declared encoding

Common XML Errors

Frequent mistakes include: unclosed tags (<p> without </p>), improper nesting (<a><b></a></b>), unescaped special characters (& should be &amp;), and missing quotes around attribute values.

Error Message Interpretation

When validation fails, you get the line number and character position where parsing stopped, plus an explanation of what the parser expected to find. This precise information helps you locate and fix issues efficiently.

Beyond Well-Formedness

Well-formed XML follows syntax rules. Valid XML additionally conforms to a schema (DTD, XSD, or RelaxNG). The validator checks well-formedness by default; schema validation requires uploading or referencing your schema definition.

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Frequently Asked Questions

What makes XML well-formed vs valid?
Well-formed XML follows syntax rules: proper nesting, matching tags, quoted attributes, single root element. Valid XML additionally conforms to a schema (DTD or XSD) defining allowed elements and structure. Our validator checks both - well-formedness first, then optional schema validation.
What are common XML validation errors?
Common errors: unclosed tags, mismatched tag names (case-sensitive!), unquoted attributes, special characters not escaped (<, >, &), multiple root elements, and invalid characters in element names. We show exact line numbers and descriptions.
How do I escape special characters in XML?
Reserved characters must be escaped: < becomes &lt;, > becomes &gt;, & becomes &amp;, ' becomes &apos;, " becomes &quot;. Or use CDATA sections for blocks of special characters: <![CDATA[content with <special> characters]]>.
What is an XML Schema (XSD)?
XSD defines allowed elements, attributes, data types, and structure. It's more powerful than DTD, supporting namespaces and complex types. Paste or upload your XSD to validate XML against specific requirements, not just syntax.
How do I validate XML with namespaces?
Namespaces prevent name collisions in complex XML. They use prefixes (xmlns:prefix="uri") and affect validation. Ensure namespace declarations are correct and match your schema. We handle default and prefixed namespaces properly.
Can I format/beautify XML while validating?
Yes! Our tool can pretty-print XML with consistent indentation while validating. This makes errors easier to spot. Choose your indentation preference (2 or 4 spaces, tabs) and get both validation results and formatted output.