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Free Online XML Validator

Check your XML syntax instantly. Get clear error messages showing the exact location of every XML syntax error — all running locally in your browser.

XML validation checks that a document conforms to the XML 1.0 specification: all tags must be properly opened and closed, attribute values must be quoted, special characters must be escaped as entities, and the document must have a single root element. Even a single misplaced angle bracket can make an entire XML document unparseable.

JSON Viewer Pro's XML validator uses the browser's native DOMParser to check your XML in real time. When an error is detected, you see the exact line and column number along with a description of the problem. The Monaco editor places a red error marker directly on the offending line so you can find and fix the issue without counting characters manually.

Common XML errors include unclosed tags, missing closing angle brackets, unescaped & characters (use &amp;), unescaped < characters outside of CDATA sections, duplicate attribute names, and invalid XML characters. The validator catches all of these and gives you a clear explanation of what went wrong and where.

Key Features

  • ✓ Real-time XML syntax validation
  • ✓ Shows exact line and column of errors
  • ✓ Human-readable error explanations
  • ✓ Detects unclosed tags
  • ✓ Detects unescaped special characters
  • ✓ Validates XML namespace declarations
  • ✓ Error markers in Monaco editor
  • ✓ No data sent to any server

Common Use Cases

  • → Validate XML before sending to APIs
  • → Check XML config file syntax
  • → Debug SOAP message errors
  • → Validate RSS or Atom feeds
  • → Check XML from external systems
  • → Validate Maven or Gradle XML files
  • → Validate Spring or Hibernate config
  • → Fix XML before importing to databases

Frequently Asked Questions

What makes XML invalid?

Unclosed tags, unescaped special characters (&, <, >), missing quotes around attribute values, duplicate attributes, or multiple root elements.

Does it validate against an XML Schema (XSD)?

Not currently. The validator checks well-formedness (XML syntax). XSD schema validation is on the roadmap.

Is validation instant?

Yes. Validation runs in real time with a short debounce, so the editor stays responsive even on large XML files.

JSON Viewer Pro — all processing runs locally in your browser. Your data is never sent to any server. Free to use, no account required.Privacy Policy·Contact