XML Well-Formedness Checker - Syntax Validator

Check if XML is well-formed according to XML 1.0 specification. Detect syntax errors and malformed tags. Browser-based, instant validation.

XML Input

Result

Paste XML and click Check

Well-Formedness Rules

Single root element
Properly nested tags
All tags closed
Attributes in quotes
Valid character encoding
No duplicate attributes

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Frequently Asked Questions

XML that follows basic syntax rules: proper nesting, matching tags, quoted attributes, and valid characters. It can be parsed but may not match any schema.

Well-formedness checks syntax. Validation checks against a schema (XSD, DTD). This tool only checks well-formedness.

Mismatched tags, unquoted attributes, invalid characters, improper nesting, missing root element, and encoding issues.

Yes. All checking happens in your browser. No data is sent to any server.

No. It reports errors with line numbers. You need to fix them manually in your source.

Namespace prefixes and declarations are checked for validity as part of well-formedness.

Paste one document at a time. For batch validation, use command-line tools like xmllint.

DTD declarations are parsed for syntax but not resolved. Remote DTDs are not fetched.

XML 1.0 and 1.1 are both supported by the browser's built-in parser.

Line numbers point to where the parser detected the error, which may be after the actual mistake.

XML Input

Result

Well-Formedness Rules

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