XML Validator
Validate XML documents for well-formedness, syntax errors, and structural issues. Get detailed error reports with line numbers, statistics, and best practice recommendations.
Results will appear here after validation
Recommended Settings
XML Validation Best Practices
- •Always include XML declaration (<?xml version="1.0" encoding="UTF-8"?>) at the start
- •Ensure all opening tags have matching closing tags or use self-closing syntax (<tag />)
- •Properly nest elements - last opened tag must be first closed (LIFO order)
- •Quote all attribute values with double quotes or single quotes consistently
- •Keep nesting depth reasonable (under 10 levels) for better readability and maintainability
Common XML Errors
- •Missing closing tags - every <tag> needs </tag> or self-close with <tag />
- •Improper nesting - tags must be properly nested, not overlapping
- •Unquoted attributes - all attribute values must be in quotes
- •Invalid characters in tag names - use letters, numbers, hyphens, underscores only
- •Multiple root elements - XML documents must have exactly one root element
Pro Tips
- •Fix errors before warnings - errors prevent parsing, warnings are best practices
- •Use example buttons to see valid and invalid XML structures
- •Line numbers in errors help you quickly locate and fix issues
- •Download validation reports for documentation and audit trails
Most Popular
Most users validate during development to catch errors early before deployment
When to Use This Tool
Validate XML during development to catch syntax errors early. Check that XML files are well-formed before deploying to production, integrating with APIs, or processing with XSLT. Essential for debugging XML parsing issues, fixing malformed data, and ensuring compatibility with XML parsers and validators.
Recommended: Development
Verify XML data quality before importing into databases or processing with ETL pipelines. Validate XML exports from legacy systems, ensure data integrity in XML-based integrations, and catch structural issues before they cause downstream failures. Critical for data migration projects and B2B data exchange.
Recommended: Data Quality
Test SOAP/XML API responses to ensure they're well-formed and match expected structure. Validate XML payloads before sending to external services, check API responses for parsing errors, and debug XML-based web service integrations. Prevents runtime errors and failed API transactions.
Recommended: API Testing
Validate XML configuration files (Maven pom.xml, Spring beans.xml, .NET configs) before deployment. Catch syntax errors in build configurations, application settings, and deployment manifests. Ensures configurations will parse correctly and prevents deployment failures due to malformed XML.
Recommended: DevOps
How It Works
Paste or type your XML document into the input field
Tool checks for XML declaration and validates its format if present
Click 'Validate XML' to start validation process
Browser's native DOMParser API parses the XML structure
Parser checks for well-formedness: balanced tags, proper nesting, valid syntax
Extracts line numbers from parser errors for precise error location
Calculates statistics: counts elements, attributes, measures nesting depth
Checks for namespaces, empty elements, duplicate IDs, and structural issues
Categorizes issues into errors (must fix) and warnings (best practices)
Displays validation status with color-coded results (green/red)
Shows detailed error list with line numbers and helpful messages
Generate downloadable validation report or copy to clipboard
All validation happens in browser - your data never leaves your device
100% Private
Files never leave your device. All processing happens locally in your browser.
Lightning Fast
Powered by Client-side JavaScript with browser's native DOMParser API for optimal performance on modern browsers.
Secure
No data collection, no tracking, no sign-up required.
Frequently Asked Questions
What is XML well-formedness?
Well-formed XML means the document follows basic XML syntax rules: all tags are properly closed, elements are properly nested, attribute values are quoted, and there's exactly one root element. This validator checks these fundamental requirements to ensure your XML can be parsed by any XML parser.
What's the difference between errors and warnings?
Errors are critical issues that make your XML invalid and unparseable (missing closing tags, improper nesting, invalid characters). Warnings are best practice issues that don't prevent parsing but may cause problems (missing XML declaration, empty elements, duplicate IDs, deep nesting). Fix errors first, then address warnings.
Does this validate against XSD schemas or DTDs?
This tool validates XML well-formedness using the browser's DOMParser API. It checks syntax, structure, and basic XML rules. It does not validate against XSD schemas or DTD documents. For schema validation, you would need additional tools that implement XSD/DTD validation engines.
Why is my XML declaration missing warning showing?
The XML declaration (<?xml version="1.0" encoding="UTF-8"?>) is optional but highly recommended. It specifies the XML version and character encoding, ensuring parsers handle the file correctly. While technically valid without it, including the declaration is considered best practice and prevents encoding-related issues.
What does maximum depth mean?
Maximum depth is the deepest level of nesting in your XML structure. For example, root > child > grandchild is depth 3. Very deep nesting (10+ levels) can make XML harder to read, process, and maintain. The validator warns when depth exceeds 10 levels, suggesting you consider flattening your structure.
Can this detect duplicate IDs?
Yes! The validator checks for duplicate ID attributes across all elements. In valid XML, each ID should be unique within the document. Duplicate IDs are reported as warnings because while they don't prevent parsing, they violate XML best practices and can cause issues with XPath queries and DOM manipulation.
How do I fix "element not closed" errors?
This error means you have an opening tag without a matching closing tag, or tags are improperly nested. Check that every <tag> has a corresponding </tag>, or use self-closing syntax <tag />. Ensure tags are nested correctly - the last opened tag must be the first closed (LIFO order).
Is my XML data sent to a server?
No. All validation happens entirely in your browser using JavaScript and the native DOMParser API. Your XML data never leaves your machine, ensuring complete privacy and security. There's no server communication, no data upload, and no external processing - everything runs 100% locally.