XML Validator

Validate XML documents with DTD and XSD schema support

XML Input

Enter or paste XML data to validate syntax and structure

Schema (Optional)

Optional: Provide a DTD or XSD schema for validation

Schema Type

Select the type of schema you're providing

Validation Results

What is XML Validation?

XML validation checks if your XML document follows correct syntax rules and optionally validates against a DTD or XSD schema. This tool validates XML entirely in your browser - your data never leaves your device. It's essential for catching errors in configuration files, SOAP messages, data exports, and any XML-based formats before deployment or processing.

How to Use

Paste your XML data into the input field
Optionally, paste a DTD or XSD schema and select the schema type
Click "Validate XML" to check for syntax and schema errors
Review any errors with line and column numbers
Use "Analyze Structure" to see document statistics
Fix errors and re-validate until your XML is correct

Example

Valid XML:

<?xml version="1.0" encoding="UTF-8"?>
<bookstore>
  <book category="fiction">
    <title>The Great Gatsby</title>
    <author>F. Scott Fitzgerald</author>
    <year>1925</year>
    <price>10.99</price>
  </book>
  <book category="science">
    <title>A Brief History of Time</title>
    <author>Stephen Hawking</author>
    <year>1988</year>
    <price>15.99</price>
  </book>
</bookstore>

Invalid XML (unclosed tag):

<?xml version="1.0"?>
<bookstore>
  <book>
    <title>Example Book</title>
    <author>John Doe
  </book>
</bookstore>

Features

Validate XML well-formedness with detailed error messages
Display error line and column numbers for easy debugging
Optional DTD (Document Type Definition) validation
Optional XSD (XML Schema Definition) validation
Analyze document structure (element count, depth, attributes)
Web Worker processing for large files (>100KB) to maintain UI responsiveness
100% client-side processing for complete privacy
Supports XML namespaces and special characters
Detect common errors: unclosed tags, mismatched elements, invalid attributes
Works with SOAP messages, configuration files, and data exports

Common XML Errors

Unclosed tags: Every opening tag must have a matching closing tag or be self-closing (<tag />).
Mismatched tags: Opening and closing tag names must match exactly (case-sensitive).
Multiple root elements: XML documents must have exactly one root element.
Invalid tag names: Tag names must start with a letter or underscore, not numbers or special characters.
Unclosed attributes: Attribute values must be enclosed in matching quotes.
Special characters: Use < > & " ' for special characters in text content.

When to Use XML Validator

Before processing XML data exports or imports
When debugging SOAP web service messages
To verify XML configuration files before deployment
When learning XML syntax and best practices
To validate XML against DTD or XSD schemas
Before converting XML to other formats like JSON
When troubleshooting XML parsing errors in applications

DTD vs XSD Validation

DTD (Document Type Definition): Older schema format that defines element structure and attributes. Simpler but less powerful than XSD. Good for basic validation of element presence and nesting.

XSD (XML Schema Definition): Modern schema format with rich data type support, namespaces, and complex validation rules. Provides more detailed validation including data types, patterns, and constraints.

Frequently Asked Questions

What is XML validation?

XML validation checks if your XML document is well-formed (follows XML syntax rules) and optionally validates against a DTD or XSD schema. It identifies errors like unclosed tags, mismatched elements, invalid attributes, and schema violations, helping you fix XML files before deployment.

What's the difference between well-formedness and validity?

Well-formedness checks basic XML syntax rules (proper tag nesting, closed tags, valid characters). Validity checks if the XML structure matches a specific schema (DTD or XSD) that defines allowed elements, attributes, and their relationships. All valid XML must be well-formed, but well-formed XML isn't necessarily valid against a schema.

Does this support DTD and XSD validation?

Yes, this validator supports both DTD (Document Type Definition) and XSD (XML Schema Definition) validation. You can optionally upload a schema file to validate your XML structure against specific requirements, ensuring it has the correct elements, attributes, and data types.

How does this differ from the XML formatter?

The validator focuses on checking correctness and providing detailed error messages with line numbers. The formatter beautifies valid XML with consistent indentation and spacing. Use the validator to find and fix errors first, then use the formatter to clean up the structure.

What types of errors does it detect?

The validator detects syntax errors including unclosed tags, mismatched opening/closing tags, invalid tag names, unclosed attributes, multiple root elements, invalid characters, and malformed structures. When using schema validation, it also detects missing required elements, incorrect element order, and missing required attributes.

Is my data sent to a server?

No, all XML validation happens entirely in your browser. Your data never leaves your device, ensuring complete privacy and security for sensitive XML files like configuration files, SOAP messages, or data exports. For large files (>100KB), processing happens in a Web Worker to keep the UI responsive.

Can it validate SOAP messages?

Yes, SOAP messages are XML documents, so this validator can check their syntax. For full SOAP validation including envelope structure and WSDL compliance, you may need additional specialized validation, but this tool will catch all XML syntax errors.

Does it support XML namespaces?

Yes, the validator fully supports XML namespaces. It correctly handles namespace declarations, prefixed elements, and default namespaces according to XML namespace specifications.

What happens with large XML files?

For XML files larger than 100KB, validation automatically runs in a Web Worker to prevent the browser from freezing. This ensures the page remains responsive even when validating very large documents like data exports or complex configuration files.

Can I validate XML fragments?

This validator requires a complete XML document with a single root element. If you have an XML fragment, wrap it in a temporary root element like <root>your fragment</root> to validate the syntax of the fragment content.