Online XML Validator [2025]

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Instantly check your XML (Extensible Markup Language) documents for syntax errors and ensure they are well-formed.

✓ Instant Well-Formedness Check✓ Detailed Error Reporting (Line/Column)✓ Uses Browser's Native Parser✓ Free & Online

XML Input

Validation Result

Enter XML and click Validate.

What is XML?

XML stands for Extensible Markup Language. It's a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable.

XML emphasizes simplicity, generality, and usability across the Internet. It's widely used for configuration files, data exchange between systems (like RSS feeds or SOAP messages), and defining document structures. Unlike HTML, XML doesn't have predefined tags; you define your own tags to describe your data.

Why Validate XML Well-Formedness?

  • •

    Ensure Parsability:

    An XML document *must* be well-formed to be successfully parsed by any standard XML parser. Syntax errors will cause parsing to fail completely.

  • •

    Prevent System Errors:

    Applications relying on XML data will break if the XML is not well-formed. Validating prevents these downstream issues.

  • •

    Basic Syntax Check:

    It catches fundamental errors like mismatched tags, incorrect attribute quoting, invalid characters, and missing root elements.

  • •

    Foundation for Further Validation:

    Before you can validate an XML document against a schema (DTD or XSD), it must first be well-formed.

Frequently Asked Questions

What does "Well-Formed" mean for XML?

A well-formed XML document adheres to the basic syntax rules defined by the XML specification. This includes having a single root element, properly nested tags, correctly quoted attributes, and valid character usage. It's the minimum requirement for an XML document to be parsable.

Does this tool validate against a DTD or XSD Schema?

No. This validator only checks if the XML document is well-formed (syntactically correct). It does not validate the document's structure or content against a specific Document Type Definition (DTD) or XML Schema Definition (XSD). Schema validation requires the schema file itself and is a more complex process, typically done server-side or with specialized tools.

Is my data secure?

Yes. All validation happens directly in your browser using the built-in `DOMParser`. Your XML data is never sent to our servers.

What happens if my XML is invalid (not well-formed)?

The validator will display an error message indicating the nature of the syntax error. It will also attempt to show the line number, column number, and the problematic source text snippet provided by the browser's parser to help you locate and fix the issue.

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